BASIS AND PURPOSE DOCUMENT FOR 

 THE DEVELOPMENT OF PROPOSED STANDARDS FOR 

 THE PRIMARY ALUMINUM INDUSTRY

 U.S. ENVIRONMENTAL PROTECTION AGENCY 

 Office of Air and Radiation 

 Office of Air Quality Planning and Standards 

 Research Triangle Park, North Carolina 27711 

 July 19, 1996 
ii 

 TABLE OF CONTENTS

 Section Page 

1.0 BACKGROUND............................................ 1 

 1.1 NATIONAL EMISSION STANDARDS FOR HAZARDOUS 

 AIR POLLUTANTS FOR SOURCE CATEGORIES............. 2 

 1.2 SELECTION OF SOURCE CATEGORY..................... 3 

 1.3 PRIMARY ALUMINUM PLANTS.......................... 4 

2.0 RATIONALE FOR THE PROPOSED STANDARDS.................. 7 

 2.1 SOURCE CATEGORY TO BE REGULATED.................. 7 

 2.2 AFFECTED SOURCES................................. 7 

 2.2.1 Selection of Affected Sources............. 7 

 2.2.2 HAPs from Affected Sources................ 9 

 2.3 POLLUTANTS FOR REGULATION........................ 11 

 

 2.3.1 Health Effects............................ 11 

 2.3.2 Measurement............................... 14 

 2.3.3 Other Pollutants.......................... 16 

 2.4 SELECTION OF MACT................................ 17 

 2.4.1 Background................................ 17 

 2.4.2 Subcategorization......................... 18 

 2.4.3 MACT Floor Technologies................... 22 

 2.4.4 Beyond MACT Floor Evaluation.............. 23 

3.0 PROPOSED STANDARDS.................................... 25 

 3.1 EMISSION LIMITS.................................. 25 

 3.2 MONITORING AND COMPLIANCE REQUIREMENTS........... 31 

 3.2.1 Potlines.................................. 34 

 3.2.2 Anode Bake Furnaces....................... 37 

 3.2.3 Paste Production.......................... 37 

 3.2.4 Emission Averaging........................ 37 

 3.2.5 Reduced Sampling Frequency................ 40 

 3.3 RECORDKEEPING AND REPORTING REQUIREMENTS......... 41 

 3.4 DELEGATION OF AUTHORITY.......................... 41 
iii 

4.0SUMMARY OF ENVIRONMENTAL, COST, ENERGY, AND 

 ECONOMIC IMPACTS...................................... 49 

 4.1 AIR QUALITY IMPACTS.............................. 49 

 

 4.2 SOLID WASTE IMPACTS.............................. 49 

 4.3 COST IMPACTS..................................... 49 

 4.4 ECONOMIC IMPACTS................................. 51 

 4.5 NON-AIR QUALITY HEALTH AND ENVIRONMENTAL IMPACTS. 51 

 4.5.1 Deposition................................ 51 

 4.5.2 Water..................................... 51 

 4.5.3 Solid Waste............................... 52 

 

 4.6 ENERGY IMPACTS................................... 52 

APPENDIX A: Rationale for Subcategorization of Sources 

 for the Primary Aluminum Industry 

APPENDIX B: Determination of MACT Floor Performance Levels 

APPENDIX C: Beyond-the-Floor Analysis 

 

APPENDIX D: Complete Listing of MACT Floor Data 
iv 

 LIST OF TABLES 

Table Page 

1 SUMMARY OF PROPOSED EMISSION LIMITS FOR EXISTING SOURCES.26 

2 SUMMARY OF PROPOSED EMISSION LIMITS FOR NEW SOURCES......30 

3 PROPOSED MONITORING AND COMPLIANCE REQUIREMENTS..........32 

4 POTLINE EMISSION LIMITS FOR EMISSIONS AVERAGING..........39 

5 BAKE FURNACE EMISSION LIMITS FOR EMISSIONS AVERAGING.....40 

6 APPLICABILITY OF GENERAL PROVISIONS TO SUBPART LL........42 
1.0 BACKGROUND

 The EPA developed this proposed air emissions rule through 

a rulemaking process known as the Share-A-MACT Program. 

Participants in the pilot program include State regulators, 

tribal governments, industry representatives, and associated 

groups including the Aluminum Association and STAPPA/ALAPCO 

(State and Territorial Air Pollution Program Administrators 

Association/Association of Local Air Pollution Control 

Officials). The partnership process included a cooperative 

effort in identifying data needs; collecting available data; 

conducting emission testing with shared funding from the EPA, 

Washington Department of Ecology, and the industry; and meeting 

with these representatives to share technical information. 

 The proposed MACT standard for primary aluminum plants 

limits emissions of hazardous air pollutants (HAPs), primarily 

hydrogen fluoride (HF) and polycyclic organic matter (POM), from 

aluminum production, paste production, and anode bake furnaces. 

The overall effect of the proposed rule would be to raise the 

control performance of nearly half of the industry to the level 

of control achieved by the best performing plants. Currently, 

over 11,000 tons per year (tpy) of total fluoride (TF) and POM 

and emitted nationwide; these emissions would be reduced by more 

than 50 percent. In addition, emissions of total particulate 

matter would be reduced by 16,000 tpy. The benefits of these 

reductions will be lower ambient air concentrations of these 

pollutants, and consequently, lower levels of exposure. The 

deposition of fluorides and POM on waters, such as the Great 

Lakes, would also be reduced. These benefits will be achieved 

with no plant closures predicted and without any significant 

adverse economic impacts on the industry. 

 The proposed standard is based on a combination of control 

techniques that either prevent the escape of emissions in the 

first place or that capture the pollutants and return them to the 

process. Over the past 20 years, many plants have already 

implemented these control techniques both to reduce emissions and 

to recover valuable fluorides, which reduces the operating costs 

of the emission control systems. 

 For the control of fugitive emissions, enhanced work 

practices and operating procedures are used to prevent the escape 

of emissions. Emissions that are collected by primary control 

systems are routed to dry alumina scrubbers (for potlines or bake 

furnaces) or dry coke scrubbers (for paste production) where the 

pollutants are captured and returned to the production process. 

Several plants will achieve emission reductions well beyond the 

nationwide average of 50 percent by replacing less efficient wet 

scrubbers with more efficient dry scrubbers and by installing 

emission controls on those anode bake furnaces and paste 

production operations that currently have no emission controls. 
2 

 The proposed rule also provides flexibility in its

requirements for monitoring the performance of the control 

techniques while ensuring the MACT level of control is achieved 

on a continuing basis. It contains provisions for reducing the 

frequency of sampling at those plants that show consistent 

performance below the level of the standard, which reduces the 

cost of monitoring. Provisions are also included to allow the 

use of innovative continuous emission monitors (CEMs) for 

hydrogen fluoride (HF) as an alternative measurement method for 

TF emissions. These new CEMs have shown promise for monitoring 

emission control and can also be used as a process tool to reduce 

operating costs by improving work practices and operating 

procedures. The rule also contains provisions for emission 

averaging, which provides owners or operators an opportunity to 

find the most cost-effective way to meet the limits at their 

particular plant. 

 The proposed rule has negligible adverse effects on energy 

consumption and secondary environmental impacts. When one plant 

replaces wet scrubbers with the highly-efficient dry scrubbers, 

the generation of sludge (solid waste) that requires disposal and 

the discharge of contaminated water will be eliminated. 

 The MACT level for new sources will have the effect of 

either discouraging the construction of Soderberg potlines, which 

emit much more of the carcinogenic POMs than do prebake potlines, 

or encouraging process changes for Soderberg potlines that will 

reduce POM and fluoride emissions to levels achieved by the best 

controlled prebake potlines. 

 The following sections of this report provide additional 

information on the standards development process for MACT 

standards; the industry and its regulatory history; the rationale 

for selection of the source category, emission sources, emission 

limits, and monitoring and compliance requirements; and the 

impacts of the proposed requirements. 

 1.1 National Emission Standards for Hazardous Air

 Pollutants (NESHAP) for Source Categories

 Section 112 of the Clean Air Act as amended requires the 

development of NESHAP for the control of emissions of HAPs from 

both new and existing major or area sources. The statute 

requires the standard to reflect the maximum degree of reduction 

in emissions of HAP's that is achievable taking into 

consideration the cost of achieving the emission reduction, any 

nonair quality health and environmental reduction, and energy 

requirements. This level of control is commonly referred to as 

the maximum achievable control technology (MACT). 
3 

 Emission reductions may be accomplished through application 

of measures, processes, methods, systems or techniques including, 

but not limited to: (1) Reducing the volume of, or eliminating 

emissions of, such pollutants through process changes, 

substitution of materials, or other modifications, (2) enclosing 

systems or processes to eliminate emissions, (3) collecting, 

capturing, or treating such pollutants when released from a 

process, stack, storage or fugitive emissions point, (4) design, 

equipment, work practice, or operational standards (including 

requirements for operator training or certification) as provided 

in subsection (h), or (5) a combination of the above [section 

112(d)(2)]. 

 1.2 Selection of Source Category

 Section 112 specifically directs the EPA to develop a list 

of all categories of all major and area sources as appropriate 

emitting one or more of the 189 HAP's listed in section 112(b). 

The EPA published an initial list of source categories on July 

16, 1992 (57 FR 31,576) and may amend the list at any time. A 

schedule for promulgation of standards for each source category 

was published on December 3, 1993 (58 FR 63941). Primary 

aluminum production is one of the 174 categories of sources 

listed. As defined in the EPA report documenting the selection 

of the source categories, this category consists of plants 

engaged in producing primary aluminum by electrolytically 

reducing alumina, including but not limited to, the following 

process units: (1) carbon mix plants, (2) reduction plants, (3) 

anode bake plants, (4) holding furnaces in the casting area, (5) 

casting processes, and (6) refining processes.1

 The listing was 

based on the Administrator's determination that primary aluminum 

plants may reasonably be anticipated to emit several of the 189 

listed HAP's in sufficient quantity to be designated as major 

sources. The EPA subsequently decided to include carbon mix 

plants, reduction plants, and anode bake furnaces in the primary 

aluminum source category and placed the other sources in a 

separate source category for secondary aluminum production. 

 

 

1

 Documentation for Developing the Initial Source Category 

List: Final Report. U.S. Environmental Protection Agency. 

Office of Air Quality Planning and Standards. EPA-450/3091-030. 

 July 1992. Pages 3-4 and A-6. 
4 

 1.3 Primary Aluminum Plants

 Primary aluminum plants produce aluminum metal through the 

electrolytic reduction of aluminum oxide (alumina) by direct 

current voltage in an electrolyte (called "cryolite") of sodium 

aluminum fluoride. A total of 23 primary aluminum plants are 

currently located in 14 States. A majority of these plants are 

concentrated in the Northwest in close proximity to hydroelectric 

power sources. 

 New source performance standards (NSPS) for primary aluminum 

reduction plants (40 CFR part 60, Subpart S) were originally 

promulgated in 1976 (41 FR 3826, January 26, 1976) and amended in 

1980 and 1989 (45 FR 44202, June 30, 1980; 54 FR 6669, February 

14, 1989). The NSPS limits emissions of gaseous and particulate 

fluorides, measured as total fluorides (TF), from all potroom 

groups and anode bake furnaces constructed, modified, or 

reconstructed after October 23, 1974. Emissions are limited to 

1.0 kg/Mg (2.0 lb/ton) of aluminum produced for potroom groups at 

Soderberg plants, 0.95 kg/Mg (1.9 lb/ton) of aluminum produced 

for potroom groups at prebake plants, and 0.05 kg/Mg (0.1 lb/ton) 

of aluminum equivalent for anode bake plants. Higher, never-tobe-exceeded limits, are allowed for potrooms at prebake plants 

(2.5 lb/ton) and Soderberg plants (2.6 lb/ton) if the owner or 

operator can establish that a proper control system was installed 

and operated and maintained in an exemplary manner.

 Monthly performance tests are required by the NSPS to verify 

compliance; less frequent testing of the anode bake plant or the 

primary control system for the potroom may be permitted if the 

owner/operator can demonstrate low emissions variability. A 

monitoring device to determine the daily weight of aluminum and 

anode produced also is required to provide information used to 

compute the emission rate of TF based on the weight of metal 

tapped during a 30-day period. Visible emissions exiting potroom 

roof monitors, determined by Method 9 observations, are limited 

to 10 percent opacity for potroom groups and 20 percent opacity 

for any anode bake plant. A total of five potlines at four 

plants are subject to the NSPS. 

 Existing facilities are subject to varying State emission 

regulations for TF developed pursuant to section 111(d) of the 

Act. A limited number of States also impose limits specific to 

sulfur dioxide (SO2) and particulate matter (PM). In some 

States, more stringent TF limits (in addition to limits for SO2

and PM) are applicable to new or modified facilities subject to 

requirements for the prevention of significant deterioration 

(PSD). Additional information on State regulations is included 

in the Technical Support Document. 
5 

 As a result of Federal and State regulations, emission 

controls are in place at all plants for the reduction cells and 

at many plants for materials handling, paste production, and 

anode bake furnaces. Emissions from materials handling are 

typically controlled by hoods and closed systems ducted to 

baghouses as a result of the NSPS for metallic mineral processing 

plants (40 CFR part 60, Subpart LL) or State rules. Emissions 

from reduction cells, paste production, and bake furnaces are 

captured by hooding and enclosure systems evacuated to a control 

device (or series of control devices) for removal of gaseous and 

particulate emissions using dry scrubbers with baghouses, wet 

scrubbers, or wet scrubbers with electrostatic precipitators. 

Thus the majority of emissions are secondary emissions from the 

reduction cells that escape capture by primary control systems. 

 The aluminum industry also is subject to effluent guidelines 

and standards set pursuant to the Clean Water Act. The EPA's 

effluent limitations for primary aluminum production (40 CFR part 

421, Subpart B) apply to fluorides and other metals, toxic 

organics, and other pollutants in wastewater generated from wet 

air pollution control systems for paste production plants, anode 

bake plants, and potlines or potrooms; as well as from anode 

contact cooling, cathode reprocessing, and aluminum casting 

operations. The discharge rules require either lime treatment of 

a bleed stream off the scrubber loop or cryolite recovery with 

lime treatment of the cryolite bleed stream if wet control 

technology is used. 

 Under the Resource Conservation and Recovery Act (RCRA)

regulations, spent potliner from primary aluminum reduction is a 

listed hazardous waste (K088) under 40 CFR 261.32, Hazardous 

Wastes from Specific Sources, due to the presence of iron cyanide 

complexes and must meet applicable RCRA requirements. Treatment 

standards for newly-listed spent aluminum potliner were proposed 

on March 2, 1995 (60 FR 11704). Hydrogen fluoride (HF) and spent 

potliner are designated as hazardous substances under section 

102(a) of the Comprehensive Environmental Response, Compensation,

and Liability Act and under section 311(b) of the Clean Water 

Act. In general, any unallowable release or discharge exceeding 

100 pounds of HF (or one pound of spent potliner) is subject to 

notification requirements under 40 CFR Parts 302 and 355. If 

more than 500 pounds of HF are present at the facility, EPA rules 

in 40 CFR Part 370 and 40 CFR 372 implementing the Emergency 

Planning and Right-to-Know-Act also may require companies to 

prepare material data safety sheets and submit annual toxic 

chemical release reports. 

 The Occupational Safety and Health Administration limits the 

concentration of fluoride dust in air to a time-weighted average 

(TWA) of 2.5 milligrams per cubic meter of air (mg/m

3

) for an 8-
6 

hour work day, 40 hour week; the concentration of HF is limited 

to 3.0 ppm. The concentration of coal tar pitch volatiles 

(benzene soluble fraction), including anthracene, benzo(a)pyrene, 

phenanthrene, acridine, chrysene, and pyrene (all POM components) 

is limited to 0.2 mg/m3

. Particulates not otherwise regulated 

(including all inert or nuisance dusts whether mineral, 

inorganic, or organic not listed specifically by substance name) 

are limited to 15 million particles per cubic foot of air 

(mppcfa) and 15 mg/m3 for the respirable fraction and 50 mppcfa 

and 15 mg/m3 for total dust (58 FR 35338, June 30, 1993). 
7 

2.0 RATIONALE FOR THE PROPOSED STANDARDS 

 2.1 Source Category to be Regulated

 Typically, primary aluminum plants are components of larger 

facilities that prepare a variety of finished products. Under 

the proposed standard, the primary aluminum source category 

excludes holding furnaces, casting, and refining processes 

because emissions from these sources are being regulated within 

the secondary aluminum source category. The EPA schedule for 

promulgation of the MACT standards (58 FR 63941, December 3, 

1993), requires rules for both the primary and secondary aluminum 

source category to be promulgated by November 15, 1997. If MACT 

standards for this source category are not promulgated by May 15, 

1999 (18 months following the promulgation deadline), Section 

112(j) of the Act requires States or local agencies with approved 

permit programs to issue permits or revise existing permits 

containing either an equivalent emission limitation or an 

alternate emission limitation for HAP control. (See Guidelines 

for MACT Determinations under Section 112(j), EPA 453/R-94-026, 

May 1994). For additional information on the secondary aluminum 

source category, contact Juan Santiago, Metals Group, Emission 

Standards Division, U.S. Environmental Protection Agency, 

Research Triangle Park, North Carolina 27711, telephone number 

(919) 541-1084. 

 2.2 Affected Sources

 2.2.1 Selection of Affected Sources. The proposed standard 

defines the affected sources as each individual potline, each 

individual anode bake furnace, and each paste production plant. 

Several factors were considered in the selection of the affected 

sources, such as ensuring that: (1) MACT is determined 

appropriately with respect to the MACT control technology and its 

performance, (2) the proposed MACT standard is implemented in a 

manner consistent with the way it was derived from the data base, 

(3) it is consistent with the development of subcategories, 

(4) it permits a clear distinction between new and existing 

sources and is appropriately related to the General Provisions, 

and (5) it provides adequate flexibility for implementation 

(e.g., emissions averaging). 

 For the aluminum reduction process, the EPA considered 

several options for defining the affected source, including 

groups of similar potlines at a plant, all potlines at a given 

plant, and each individual potline. For bake furnaces, the 

options included all bake furnaces and each bake furnace 

individually. For paste plants, the only option considered was 

for each paste production plant because no facility has more than 

one paste production operation. The options under consideration 
8 

for potlines and bake furnaces were important because they affect 

how the MACT floor and MACT are determined from the available 

data, the applicability of the new source MACT standard (what 

constitutes a new or reconstructed source), and implementation of 

emissions averaging. 

 The selection of each potline, bake furnace, and paste plant 

as the affected sources ensures that the MACT control 

technologies, which are different for each of the affected 

sources, are implemented. This approach is consistent with the 

way measurements were made and the type of data that were 

submitted, i.e., to characterize the emission control performance 

of each individual potline, each bake furnace, and each paste 

plant. The subcategories for aluminum production were based most 

reasonably on types and characteristics of individual potlines 

rather than groups of potlines. This permitted the MACT floor to 

be determined based on the average (median) performance of the 

top five potlines in each subcategory. The MACT determination 

would have been more difficult and less effective if it had been 

based on the entire group of potlines at each of the plants. 

This approach also ensures that if a new potline, bake furnace, 

or paste plant is built, it would be subject to MACT for new 

sources, which is consistent with the way the new source limit 

was derived. This approach does not limit the flexibility in 

implementing emissions averaging, which has been included as a 

provision of the rule. 

 There was concern that the selection of the affected source 

as an individual potline could subject an existing potline that 

is rebuilt to the new source MACT, even if it were infeasible for 

the rebuilt potline to meet the standard. However, the General 

Provisions address this by stating that a source is not 

considered reconstructed and subject to new source MACT unless 

"it is technologically and economically feasible for the 

reconstructed source to meet the relevant standard." 

Consequently, if the owner or operator of an existing potline 

that is rebuilt shows that it is technologically or economically 

infeasible to met the new source MACT, the potline would not be 

considered to be reconstructed and would not be subject to the 

new source limit. 

 If a new potline (or bake furnace) is built, it would 

reasonably be expected to have no technical or economical problem 

with achieving new source MACT. Consequently, the definition of 

each individual potline (or bake furnace) as the affected source 

ensures that new potlines (or bake furnaces) must meet the more 

stringent limits for new sources. If the affected source had 

been defined as the group of potlines at a plant, a potline of 

entirely new construction would not necessarily have to meet new 

source limits. 
9 

 After considering all of these factors, the individual 

potline, bake furnace and paste plant were selected as the 

affected sources. The major considerations were consistency with 

the available data, data analysis, and subcategorization (by 

potline); a clear and reasonable distinction between existing and 

new or reconstructed sources, and no loss of flexibility in 

implementing the rule. 

 2.2.2 HAPs from Affected Sources. Potlines of reduction 

cells comprise the largest source of HAP emissions in the primary 

aluminum category. HF, one of the major HAPs of concern, is 

generated from the fluoride compounds used in aluminum 

production. Emissions that are not collected by the primary 

system are released in the potroom where they mix with the 

ventilation air and escape through the roof monitor at most 

plants. The basic process operations that create secondary 

emissions include charging alumina to the bath, periodically 

removing the molten aluminum ("tapping"), replacing the anode, 

and correcting "anode effects", usually by adding more alumina 

and mixing the bath. Approximately 6,400 tpy of TF are emitted 

from potlines. POM and other organic compounds are introduced 

into the process primarily by the use of coal tar pitch in the 

anodes. POM emissions (measured as methylene chloride 

extractables) are estimated at 3,300 tpy. 

 During the MACT test program, additional analyses were made 

to quantify 20 individual POM compounds. Tests at two Soderberg 

plants showed these compounds were emitted at a rate of 0.5 to 

0.6 pound per ton (lb/t) compared to levels less than 0.01 lb/t 

from tests at two prebake plants.2

 Additional emission tests 

also were performed by the industry and provided to the Agency 

for analysis. 

 

 The anode paste plant (also known as the "green mill") 

produces anode paste or briquettes for Soderberg cells, cathode 

paste, or green pressed anodes (baked in the anode furnace) for 

prebake cells. In prebake plants, multiple anodes are formed and 

baked prior to use and the anodes are consumed in the reduction 

process. In the Soderberg process, a single mass of paste or 

briquettes of coke and pitch forms the anode. Because the anode 

is baked in place, plants using the Soderberg process do not have 

anode bake furnaces. 

 

 

 

2

 Primary Aluminum Industry - Draft Technical Support 

Document for Proposed MACT Standards (Preliminary Review Draft). 

 U.S. Environmental Protection Agency. Office of Air Quality 

Planning and Standards. February 1995. 
10 

 To make the paste, solid raw materials (calcined petroleum 

coke, anthracite coal, and pitch, as required for the various 

types of pastes) are received in bulk and transported to carbon 

plant storage. Dry solids are drawn from the sized mix bins in 

controlled proportions either in weighed batches for batch mixers 

or continuously for continuous mixers. Mixers are jacketed and 

heated with either steam or oil. For baked anode pastes, the 

mixer feed contains either solid crushed coal tar pitch or hot 

liquid pitch as a binder. The prebake paste is then transferred 

to the anode molds for forming by hydraulic or vibratory 

compaction. For Soderberg paste, a liquid pitch is metered to 

the mixers and the hot paste is discharged to transfer cars for 

transfer to the potrooms or cooled and formed into briquettes. 

POM is the major HAP emitted from paste production with 

nationwide emissions (measured as methylene chloride 

extractables) estimated at 230 tpy. Testing at two paste plants 

showed that uncontrolled emissions of the 20 targeted POM 

compounds were about 0.07 lb/t of paste. 

 Paste production and bake furnaces may be together in the 

same building, in separate buildings or series of separate 

buildings, or off-site. Under the proposed rule, an independent 

manufacturer of anodes with a paste production or an anode bake 

furnace located off-site may be subject to the requirements of 

the rule if HAPs are emitted at level constituting a major 

source. 

 Nearly all of the anodes produced for prebake plants are 

baked in open-top ring furnaces. Each ring furnace consists of a 

number of indirectly fired sunken ovens or open-topped, brick 

pits arranged in rows. Some of the spaces in the brickwork are 

mortared while others are left open intentionally. A large pipe 

or duct circles the furnace and leads to an exhaust fan. Doublesealed manholes (at least one per furnace section) are spaced 

along the top of the duct. The pits are filled with green anodes 

and petroleum coke or other insulating material is placed over 

the anodes from an overhead hopper to cover and insulate the 

anodes. After firing and cooling, the packing coke is removed 

from the pits by vacuuming or other means and reused. 

 HF and POM are the major HAPs emitted from the anode bake 

furnace stack. HF emissions originate from the recycling of 

anode butts when fluorides not removed during cleaning of the 

butts are volatilized in the furnace and removed with the flue 

gas stream. The amount of HF emitted depends on the quantity of 

anode butts recycled, the cleanliness of the butts, and the 

efficiency of the emission control device (if present). The 

amount of particulate matter emitted can vary widely, dependent 

on the type of furnace, fuel (gas or liquid), the age of the 

brickwork, packing material, and firing conditions. Particulate 
11 

matter released consists mainly of condensed tar attached to dust 

released through openings in the brick work or from the placement 

and removal of packing coke. POM emissions originate from the 

coal tar pitch used as the binder and evolve as the green anode 

is baked in the furnace. Anode bake furnaces emit about 700 tpy 

of TF (the vast majority of which is gaseous or hydrogen fluoride 

from uncontrolled bake furnaces) and 550 tpy of POM measured as 

methylene chloride extractables. Tests at two bake furnaces 

showed that the 20 targeted POM compounds were generated at a 

rate of 0.3 to 0.9 lb/t of anode prior to control by dry alumina 

scrubbers. 

 2.3 Pollutants for Regulation

 2.3.1 Health Effects. Hydrogen fluoride is a very 

corrosive and toxic inorganic acid that can be in gas or liquid 

in anhydrous form or in aqueous solution (with water). Liquid HF 

can severely burn the skin and eyes. Skin contact with anhydrous 

HF (liquid or gaseous) or solutions above 50 percent produce 

immediate pain and tissue damage as the fluoride ion can 

penetrate the skin and attack underlying tissues and bone. 

Inhalation is particularly hazardous because HF readily dissolves 

in the mucous membranes of the upper respiratory tract, nose, and 

throat. Hydrogen fluoride also is highly reactive, and in many 

cases, the reaction products also are hazardous.3

 While the human health effects of inhaling moderate amounts 

or the very low concentrations of HF that are typical at modern, 

well-controlled primary aluminum plants are not well known, 

animal tests have shown that exposure through inhalation for 

several months can result in damage to kidneys and nervous system 

changes such as learning problems. Inhalation of HF or fluoridecontaining dusts for longer periods (e.g. several years) can also 

result in bone disease, known as skeletal fluorosis. Inhalation 

of large amounts can be harmful to the heart and lungs or fatal.4

 

 The Agency for Toxic Substances and Disease Registry (ASTDR) 

reports in their 1993 toxicological profile that acute inhalation 

in combination with dermal exposure has resulted in pulmonary 

edema, pulmonary hemorrhagic edema, and tracheobronchitis. 

 

 

3

 Hydrogen Fluoride Study: Report to Congress under section 

112(n)(6) of the Clean Air Act as amended. EPA 550-R-93-001. 

September 1993. 

 

4

 Toxicological Profile for Fluorides, Hydrogen Fluoride, and 

Fluorine. U.S. Department of Health and Human Services. Public 

Health Service. TP-91/17. April 1993. 
12 

In one study cited, a significant population (about 20 percent) 

exposed to airborne HF near an aluminum plant reported nausea and 

diarrhea. The ASTDR has not established a minimal risk level 

(MRL) for inhalation or oral exposure to HF for any exposure 

duration or system category because exposure data in humans is 

not well quantified. However, existing data indicate that 

subsets of the population may be unusually susceptible to the 

toxic effects of fluoride and its compounds, including the 

elderly, persons with deficiencies of calcium, magnesium, or 

vitamin C, and people with cardiovascular and kidney problems.5

 

 The EPA oral reference dose (RfD) assessment and inhalation 

reference concentration (RfC) assessment for HF are currently 

undergoing Agency review6. Additional information on the health 

effects of HF and related gases can be found in the literature 

review contained in the EPA report, "Summary Review of Health 

Effects Associated with Hydrogen Fluoride and Related 

Compounds."7

 In the 1974 NSPS background information document, EPA 

reported documented evidence showing that fluorides emitted from 

industrial plants are responsible for damage to commercially 

grown flowers, fruits, and vegetables. However, even at the 

reduced levels emitted today, fluorides in low concentrations can 

be absorbed by grasses and plants and by animals that feed on the 

forage. Hydrogen fluoride also is a corrosive gas capable of 

property damage. For these reasons, several States require 

plants to monitor for fluoride damage in areas surrounding the 

plants. Additional information on the damage to vegetation, 

soil, wildlife, and livestock (and the critical load limit needed 

to prevent new damage) is available in the recent "Effects Study" 

conducted by Norwegian aluminum plants and the Norwegian Research 

Council.8 

 

 

5

 Reference 4. 

 

6

 Integrated Risk Management System (IRIS). Hydrogen 

Fluoride and Fluorine. U.S. Environmental Protection Agency. 

Printout dated March 8, 1995. 

 

7

 Summary Review of Health Effects Associated with Hydrogen 

Fluoride and Related Compounds: Health Issue Assessment. U.S. 

Environmental Protection Agency. Environmental Criteria and 

Assessment Office. EPA-600/8-89-002F. December 1988. 

 

8

 The Norwegian Aluminum Industry and the Local Environment: 

 Summary Report on the Project to Study the Effects of Industrial 

Emissions from Primary Aluminum Plants in Norway. Hydro 

Aluminum, Elkem Aluminum, and Sor-Norge Aluminum in cooperation 

with the Norwegian Research Council. ISBN 82-993305-0-5. 
13 

 Deposition of POM on waters such as the Great Lakes and 

Chesapeake Bay from aluminum plants also is of concern as 

discussed in the Great Waters Report to Congress.9 In the 

report, major aluminum plants are identified as significant 

sources of polycyclic aromatic hydrocarbons (PAH), including 

those aluminum plants located adjacent to or near the Great Lakes 

and those at long distances from the waterbody. Primary aluminum 

plants also are identified as one of the MACT source categories 

potentially emitting Great Waters pollutants of concern. 

 The term "coal tar pitch volatiles" denotes the complete 

class of fused polycyclic hydrocarbons that volatilize from 

pitch. These compounds are high molecular weight polycyclic 

aromatic compounds (four, five, and six benzene rings) whose 

normal state is particulate rather than gaseous. As such they 

are part of a larger class of compounds called POM (defined in 

the Act as including organic compounds with more than one benzene 

ring and which have a boiling point greater than or equal to 

100°C.) Emission test results reveal that POM compounds may 

include a combination of known HAPs such as anthracene, 

benzo(a)pyrene, and naphthalene, among others. POM is introduced 

into the process primarily by coal tar pitch. The pitch is 

produced from the refining of coal tar and is recovered as a 40- 

to 60-percent bottoms fraction of heavy organics with very high 

boiling points. 

 Many of the compounds found in POM also are known (and 

sometimes measured as) PAH. PAHs are a group of chemicals that 

are formed during the incomplete burning of coal, oil and gas, 

garbage, and other organic substances. However, all 15 compounds 

considered to be PAH in the 1990 ASTDR toxicological profile10

were found in the analytical results of POM emission tests for 

potlines, bake furnaces, and paste production. The ASTDR study 

confirms the presence of PAH at aluminum production plants and 

states: 

 

November 1994. 

 

9

 Deposition of Air Pollutants to the Great Waters: First 

Report to Congress. U.S. Environmental Protection Agency. 

Office of Air Quality Planning and Standards. 

EPA-453/R-93-055. May 1994. 

 

10 Toxicological Profile for Polycyclic Aromatic Hydrocarbons. 

 U.S. Department of Health & Human Services. Public Health 

Service. Agency for Toxic Substances and Disease Registry. TP90-20. December 1990. Pages 3, 15, 58, 96. 
14 

... Several of the PAHs, including 

benzo(a)anthracene, benzo(a)pyrene, 

benzo(b)fluoranthene, benzo(k)fluoranthene, 

chrysene, dibenzo(a,h)anthracene, and 

indeno(1,2,3-cd)pyrene, have caused tumors in 

laboratory animals when they ate them, when they 

were applied to their skin, or when they breathed 

them in the air for long periods of time. Reports 

on humans show that individuals exposed by 

breathing or skin contact for long periods of time 

to mixtures of other compounds and PAH can also 

develop cancer.11

And, 

Evidence exists to indicate that certain PAHs are 

carcinogenic in humans and animals. The evidence 

in humans comes primarily from occupational 

studies where workers involved in such processes 

as coke production, roofing, oil refining, or coal 

gasification are exposed to mixtures containing 

PAHs... Cancer associated with exposure to PAH 

containing mixtures in humans occurs predominately 

in the lung and skin following inhalation and 

dermal exposure, respectively....12

 The report also discusses the presence of respiratory tract 

tumors observed in rats that inhaled a combination of 

benzo(a)pyrene (a component of POM) and SO2. The study results 

indicated that benzo(a)pyrene is carcinogenic to animals when 

inhaled and that "the carcinogenicity can be enhanced with 

concurrent exposure to gases and particulates commonly found in 

the environment."13

 

 

 Specific populations that may be susceptible to the toxic 

effects produced by exposure to PAHs include: the unborn, people 

with nutritional deficiencies, genetic diseases, immunodeficiency 

due to age or disease, people who smoke, those with a history of 

excessive sun exposure, people with liver and skin disease, and 

women, especially of child-bearing age. There may be an 

increased risk of developing lung cancer following prolonged 

inhalation of PAH-contaminated air and skin cancer following 

 

 

11 Reference 10. Pages 3, 15, 58, 96. 

 

12 Reference 10. Pages 3, 15, 58, 96. 

 

13 Reference 10. Pages 3, 15, 58, 96. 
15 

concurrent dermal exposure to PAHs and sunlight.14 The EPA is 

currently in the process of reviewing a carcinogenicity 

assessment for POM.15

 

 2.3.2 Measurement. Historically, the combination of 

gaseous and particulate fluorides emitted from aluminum plants 

have been measured and regulated as emissions of total fluoride 

or "TF". Methods 13A and 13B, originally promulgated in 1975, 

have been used for TF sampling and analyses, along with Method 14 

which specifies the equipment and sampling procedures for 

emission testing of potroom roof monitors. 

 Traditionally, fluoride captured by the front-half filter 

has been called "particulate fluoride," and fluoride captured in 

the back-half impingers has been called "gaseous fluoride" (GF). 

However, the method has been validated only as a measure of TF 

expressed as the sum of the front-half and back-half catches. 

Thus, TF has been used for many years as a surrogate to represent 

this mixture of gaseous and particulate fluorides, and most 

emissions data currently available result from sampling and 

analysis for TF. 

 During the development of the proposed standards, EPA 

discussed with State and industry representatives various options 

for measuring gaseous HF, the listed HAP, and the use of GF or TF 

as surrogate measures for HF. Several factors were considered in 

these discussions that led to the choice of TF as a measure of 

emission control performance. A major consideration was the 

absence of a validated, accurate method for the measurement of HF 

or GF. EPA studies in the development of Method 13 identified 

problems in attempts to obtain an accurate split between 

particulate and gaseous fluoride. Hydrogen fluoride is highly 

reactive and reacts with glass in the sampling probe to form 

silicon tetrafluoride. The reactivity of HF has also been a 

problem in developing an analytical standard; currently, there is 

no EPA analytical standard that can be used to determine the 

accuracy of attempts to measure HF. During sampling, particulate 

matter in the front half of the train adsorbs GF, where it is 

then measured as particulate fluoride. Fine particulate matter 

that passes through the filter is measured as GF in the back half 

of the train. These factors produce confounding effects in 

attempts to measure HF or GF with biases in different directions. 

 

 

14 Reference 10. Pages 3, 15, 58, 96. 

 

15 Integrated Risk Management System (IRIS). Polycyclic 

Organic Matter. U.S. Environmental Protection Agency. March 10, 

1995. 
16 

 In addition, the quantity of HF or GF that is formed is affected 

by humidity and the water content of raw materials.

 A large historical data base for TF was available to 

characterize the emission control performance of the industry, to 

identify the best controlled potlines, and to develop the MACT 

floor and MACT level of control. There was a discussion among 

many different parties as to whether the MACT performance 

standard should be based on TF or GF, and EPA concluded that TF 

provides the most defensible basis to ensure that the MACT level 

of control is achieved. However, EPA recognizes the importance 

of identifying the contribution of gaseous HF to adverse health 

effects when exposure modeling is performed in the future. 

Consequently, the split between particulate and gaseous fluoride 

from Methods 13A and 13B will continue to be reported, and an 

attempt will be made to improve the accuracy and consistency of 

this determination. In addition, EPA is encouraging the 

development and application of HF CEMs as an improved monitoring 

tool for HF emissions. 

 The choices for measuring POM included expensive sampling 

and analysis to identify and quantify each of the numerous 

individual compounds that might be present or to develop a 

reasonable surrogate measure for POM. During the MACT test 

program jointly funded by the EPA, the State of Washington 

Department of Ecology, and the industry, sampling and analysis 

were performed for both individual species and for a surrogate 

measure. The surrogate approach uses methylene chloride 

extractables from both the front and back halves of a modified 

Method 5 procedure. The testing program indicated that methylene 

chloride extractables provided an adequate surrogate measure of 

the total POM species at a fraction of the cost associated with 

speciation. Consequently, the MACT level of POM control was 

defined from data for methylene chloride extractables, and the 

method developed during the test program is being proposed for 

POM compliance determinations. 

 2.3.3 Other Pollutants. Primary aluminum plants also 

discharge significant quantities of nonHAP pollutants such as 

SO2, PM, and greenhouse gases (such as tetrafluoromethane, 

hexafluoroethane, and carbon dioxide). 

 Sulfur is introduced into the aluminum production process 

primarily by the coke and pitch used to produce anodes; 

consequently, most plants limit SO2 emissions by specifying the 

maximum sulfur content they will accept in these raw materials. 

Two plants use SO2 scrubbers following the dry alumina scrubbers 

of the primary control system to obtain additional SO2 control, 

and four plants use wet roof scrubbers that provide some control 

of SO2 in secondary (fugitive) emissions. These plants and 
17 

control devices for SO2 would not be affected by the proposed 

standard. Four plants use wet systems for their primary control 

device to limit emissions of fluorides, POM, other particulate 

matter, and SO2. If these plants install dry alumina scrubbers 

to meet the MACT standard and do not keep a wet scrubber 

following the alumina scrubber, an increase in SO2 emissions 

would be expected. However, this analysis assumes that current 

SO2 requirements will remain in place even if dry alumina 

scrubbers were installed at these four plants. 

 The greenhouse gases tetrafluoroethane and hexafluoroethane 

are generated during anode effects in the reduction cell. 

Reducing the frequency and duration of anode effects will 

decrease fluoride emissions as well as emissions of these 

greenhouse gases. The EPA's Global Change Division in the Office 

of Atmospheric Programs has a voluntary program underway and is 

working with the aluminum industry to reduce emissions of these 

greenhouse gases. 

 2.4 Selection of MACT

 2.4.1 Background. After EPA has identified the specific 

source categories or subcategories of major sources to regulate 

under section 112, it must set MACT standards for each category 

or subcategory. Section 112 establishes a minimum baseline or 

"floor" for standards. For new sources, the standards for a 

source category or subcategory cannot be less stringent than the 

emission control that is achieved in practice by the bestcontrolled similar source. [Section 112(d)(3)]. The standards 

for existing sources can be less stringent than standards for new 

sources, but they cannot be less stringent than the average 

emission limitation achieved by the best-performing 12 percent of 

existing sources for categories and subcategories with 30 or more 

sources, or the best-performing 5 sources for categories or 

subcategories with fewer than 30 sources. 

 After the floor has been determined for a new or existing 

source in a source category or subcategory, the Administrator 

must set MACT standards that are no less stringent than the 

floor. Such standards must then be met by all sources within the 

category or subcategory. 

 In establishing the standards, EPA may distinguish among 

classes, types, and sizes of sources within a category or 

subcategory [section 112(d)(1)]. For example, the Agency could 

establish two classes of sources within a category or subcategory 

based on size and establish a different emissions standard for 

each class, provided both standards are at least as stringent as 

the MACT floor for that class of sources. 
18 

 The next step in establishing MACT standards is 

traditionally the investigation of regulatory alternatives. With 

MACT standards, only alternatives at least as stringent as the 

floor may be selected. Information about the industry is 

analyzed to develop model plant populations for projecting 

national impacts, including HAP emission reduction levels, costs, 

energy, and secondary impacts. Several regulatory alternative 

levels (which may be different levels of emissions control, 

different levels of applicability, or both) are then evaluated to 

select the regulatory alternative that best reflects the 

appropriate MACT level. 

 The selected alternative may be more stringent than the MACT 

floor, but the control level selected must be technically 

achievable. In selecting a regulatory alternative that 

represents MACT, EPA considers the achievable emission reductions 

of HAP's (and possibly other pollutants that are co-controlled), 

cost and economic impacts, energy impacts, and other 

environmental impacts. The objective is to achieve the maximum 

degree of emissions reduction without unreasonable economic or 

other impacts [section 112(d)(2)]. The regulatory alternatives 

selected for new and existing sources may be different because of 

different MACT floors, and separate regulatory decisions may be 

made for new and existing sources. 

 Under the Share-A-MACT approach applied during the

development of the proposed standards, EPA met with

representatives from State agencies, tribal governments, and 

industry groups to discuss the regulatory alternatives and 

associated issues. This approach to standards development allows 

EPA to select an alternative based on consensus with State 

partners and the sharing of technical data and analyses with 

other partners. For this pilot project, EPA met on several 

occasions with different groups in different locations to seek 

their views and selected an alternative using a mixture of 

analytical and consensus-based decisions. 

 2.4.2 Subcategorization. Primary aluminum operations are 

differentiated by the type of anode used and the method by which 

the anode is introduced into the reduction cell. In the prebake 

process, used by 17 plants, pots are classified as center-worked 

prebake (CWPB) or side-worked prebake (SWPB), depending on where 

the pot working (crust breaking and alumina addition) takes 

place. Soderberg pots are differentiated by the position of the 

current carrying studs in the anodes, which may be inserted 

vertically (VSS) or horizontally (HSS). Emission data reveal 

there is a clear difference in the level of POM emissions from 

prebake and Soderberg plants. 
19 

 Section 112(d) of the Act requires EPA to establish emission 

standards for each category or subcategory of major and area 

sources. Section 112(d)(1) of the Act states that "the 

Administrator may distinguish among classes, types, and sizes of 

sources within a category...in establishing such standards...." 

In establishing subcategories, EPA has considered factors such as 

air pollution control engineering differences, process operations 

(including differences between batch and continuous operations), 

emission characteristics, control device applicability, and 

opportunities for pollution prevention. For the subcategories of 

potlines, the distinctions are based primarily on differences in 

the process operation, process equipment, emissions, and the 

applicability of control devices. 

 The EPA's analysis of existing aluminum production process 

and operations resulted in the designation of seven subcategories 

for potlines. These are: (1) CWPB1 potlines; (2) CWPB2 potlines; 

(3) CWPB3 potlines; (4) SWPB potlines; (5) VSS1 potlines; 

(6) VSS2 potlines, and (7) HSS potlines. Additional information 

on the subcategorization is included in Appendix A to this 

document. 

 Prebake and Soderberg are two distinctly different processes 

for aluminum reduction that present different challenges for 

capturing emissions from the aluminum reduction cells. These two 

processes also have different characteristics, especially with 

respect to POM emissions. A major difference between the two 

processes is that the anodes used in the prebake process have 

been formed and baked in a separate process operation (i.e., the 

anode bake furnace), whereas the Soderberg process bakes the 

anode in the reduction cell as part of the production operation. 

 This difference directly affects emissions and results in larger 

quantities of organic compounds such as POM being emitted from 

the Soderberg process. 

 Other differences between the two processes also affect 

emissions and their control. In the prebake process, spent 

anodes are periodically removed and replaced, and this operation 

directly affects secondary (fugitive) emissions. Conversely, 

"green" paste (a mixture of unbaked coke and pitch) is added in a 

semi-continuous manner to the Soderberg reduction cell to allow 

it to be baked in place and to replace the anode as it is 

consumed. In addition, there are differences in the type and 

efficiency of hooding used for the two processes. In general, 

the hoods used for the Soderberg process have lower capture 

efficiencies because the gases evolving from the Soderberg cell 

are more difficult to capture. 

 Within the prebake process, center-worked (CWPB) and sideworked (SWPB) units have significant differences in design of the 
20 

equipment, its operation, and applicable emission controls, 

especially in the capture of primary emissions. The process and 

operational differences include the placement of the anodes, the 

type of side shields, the method of alumina addition, and how the 

reduction cells are worked. 

 In the SWPB process, alumina is added along the sides of the 

reduction cell and the anodes are set close together near the 

center line. In the CWPB process, alumina is added down the 

center of the pot and the anodes are closer to the side. 

Consequently, the covers and hoods for the primary collection 

system are different for these two types of units because of the 

design, placement of anodes, and working the bath from the center 

versus from the side. In addition, the newer CWPB units can be 

equipped with computer-controlled crust breakers and point 

feeders, which often allow them to be worked without removing the 

side shields. 

 The design and operational differences between SWPB and CWPB 

result in different design considerations for the primary system. 

 In general, emissions from the CWPB reduction cells can be 

captured with a higher efficiency than those from SWPB cells. 

 The investigation of the CWPB process indicates that there 

are two different designs that directly affect the ability of the 

operator to control emissions. One group is composed of CWPB 

reduction cells that are larger, generally newer, and operate at 

higher amperages (called CWPB1) than the older and smaller CWPB 

units (labeled CWPB2). The major factor affecting the difference 

in emissions and controls for the two types of units is the 

number of anode changes required. 

 Data were obtained from industry surveys on the frequency of 

changing anodes.16 These data indicate that the older and smaller 

CWPB2 cells have more frequent anode changes per ton of aluminum 

than do the newer and larger CWPB1 cells. More frequent anode 

changes result in greater quantities of secondary (fugitive) 

emissions that are difficult to capture and control. 

 There are two other differences between the large and small 

CWPB units that affect emissions and their capture. Access is 

required more often to the smaller units because they are 

generally more unstable and are less likely to have computer 

controls. More frequent access means the shields of the primary 

collection system are opened more frequently and perhaps for 

 

 

16 K. Ours, Research Triangle Institute, to Docket. 

Memorandum on Summary of Information for ICR-1 and ICR-2. 

September 30, 1993. 
21 

longer periods, which results in poorer emission capture and 

higher emissions. Another factor is the smaller units generally 

have more anodes per reduction cell, which affects the design and 

capture efficiency of the hooding. These combinations of factors 

indicate that the larger CWPB units have lower emissions per ton 

of aluminum produced and that less emissions escape capture by 

the primary collection system. 

 Four center-worked prebake potlines with wet primary control 

systems were assigned a separate subcategory (CWPB3). These 

potlines produce a high purity aluminum for a specialized market, 

and they can do so only because metal impurities are removed with 

the sludge from the wet scrubbers. If these potlines were 

required to install dry alumina scrubbers, the contaminants would 

be returned to the reduction cell and contaminate the aluminum. 

The company claims that if they must meet MACT for the prebake 

subcategory of modern potlines with dry alumina scrubbers, they 

could lose their market for high purity aluminum. The EPA is 

requesting comments on the issue of a separate subcategory for 

plants that produce high purity aluminum. 

 There are two distinct designs used in the Soderberg 

process: horizontal (HSS) and vertical stud (VSS). The VSS 

design has steel studs that carry electrical current vertically 

through the unbaked paste and into the baked portion of the 

anode. In the HSS design, the studs project horizontally. The 

differences in design and operation result in different types of 

hooding and evaluation rates, both of which affect emissions and 

controls. In the VSS cells, the stationary anode casing and 

vertical projection of the studs through the anode allow the 

installation of a gas collection skirt between the anode casing 

and bath. The collected gases are ducted to burners where carbon 

monoxide, tars, and other hydrocarbons are burned prior to the 

primary control device. 

 The design of the HSS cell prevents the installation of an 

integral gas collection device because the anode casing is formed 

by removable channels that support the studs, and these channels 

must be periodically changed as the anode moves downward. 

Consequently, the hooding for the HSS cell is restricted to a 

canopy suspension, which results in air infiltration and 

dilution. The collected gases from the HSS cell are too dilute 

to support combustion in burners. For comparison, a typical VSS 

cell has an evacuation rate on the order of 500 ft3

/min compared 

to a range of 3,500 of 5,000 ft3

/min for an HSS cell. 

 Two VSS plants with five potlines use wet roof scrubbers to 

control secondary emissions, and the third plant also with five 

potlines uses work practices for secondary emission control. 

Consequently, EPA investigated the use of wet roof scrubbers as 
22 

the MACT floor technology for all VSS plants. However, data 

obtained from one plant with wet roof scrubbers indicated that 

their scrubbers were shut down in periods of cold weather to 

avoid damage to the scrubbers and water treatment plant. The 

data indicated that the scrubbers were shut down due to cold 

weather an average of 36 days per year (a range of 19 to 48 days 

per year from 1986 to 1993). This represents a down time of 10 

percent, i.e., they operated about 90 percent of the year. The 

procedure is to shut the scrubbers down when the temperature 

reaches 27°F and the temperature is predicted to drop further.

 The VSS plant without wet roof scrubbers is located in 

northern Montana where the weather is much colder. Data obtained 

from the National Weather Service indicated that the normal daily 

average temperature was below 27°F about 21 percent of the time 

and the normal daily low temperature was below 27°F about 40 

percent of the year. Consequently, the use of wet roof scrubbers 

based on the other plant's experience suggests that scrubbers 

installed in northern Montana could be shut down on the order of 

20 to 40 percent of the time. Consequently, EPA determined that 

wet roof scrubber technology has not been adequately demonstrated 

for very cold climates. 

 The EPA believes that the technical feasibility of emission 

controls is an important consideration when evaluating the need 

to develop subcategories. For this case, EPA concluded that wet 

roof scrubbers were not applicable or feasible as the MACT floor 

technology for the VSS plant in Montana. Consequently, a 

separate subcategory (VSS2) was created for the five potlines at 

the plant in Montana, and the MACT floor for this subcategory 

would be determined by the average emission limitation achieved 

by these five potlines. 

 Because of the air pollution control engineering 

differences, including consideration of the variations in process 

operation, emission characteristics, and control device 

applicability, EPA developed separate MACT floors for each of 

these subcategories of potlines. 

 The vast majority of anode bake furnaces are similar in 

emissions potential and the applicability of emission control 

devices. One exception that exists is an anode bake furnace that 

is not located on the same site as the primary aluminum 

production facility. This facility does not have access to 

alumina for use in the dry alumina scrubber, and it does not have 

potlines that can use the reacted alumina generated by a dry 

alumina scrubber. On the other hand, bake furnaces co-located 

with the primary aluminum potlines have access to alumina, the 

basic raw material used for aluminum production, and can transfer 

the reacted alumina from the dry scrubber to the reduction cells. 
23 

 Consequently, a separate subcategory was created for this offsite bake furnace because the emission control technology (dry 

alumina scrubbers) would not be applicable. 

 2.4.3 MACT Floor Technologies. In general, the control 

option for primary emissions is the installation of highlyefficient dry alumina scrubbers at those plants that do not have 

them. Dry alumina scrubbers use alumina ore to adsorb gaseous 

pollutants and a baghouse to remove particulate pollutants and 

the alumina. This system controls 99.5+ percent of the fluoride 

emissions and 90 to 99 percent of the POM emissions at the best 

controlled plants. Consequently, this control device represents 

the MACT floor technology and the best control for primary 

emissions. 

 The MACT floor technology associated with the control of 

secondary emissions includes the use of wet roof scrubbers for 

SWPB and VSS1 potlines and, for all subcategories, adherence to 

specific work practices such as high draft on open pots, 

operating conditions, equipment inspection, maintenance, and 

repair. 

 Several control devices are currently in use for the 

control of emissions from paste production. Dry coke scrubbers 

are used at five plants to control POM emissions, and the other 

plants use various types of controls for specific emission points 

in paste production. The dry coke scrubber is the most effective 

of these control devices (shown to achieve up to 99.8 percent 

control of POM emissions) because the coke (carbon) provides a 

condensation point for the organic vapors generated during paste 

production, and a baghouse is used to control fine particulate 

matter and to remove coke fines. The coke can be returned 

directly to the paste production operation. Given that there are 

less than 30 plants, EPA examined the top five best performing 

plants. Based on the top five plants, the dry coke scrubber was 

identified as the MACT floor technology for paste production. 

 The most common and effective control device currently used 

for anode bake furnaces located at primary aluminum plants is the 

dry alumina scrubber, used by 12 of the 17 plants with anode bake 

furnaces. Two plants use an electrostatic precipitator (ESP) and 

three plants do not use a control device. The dry alumina 

scrubber is the most effective of these control devices because 

the alumina is an adsorbent for the HF gas generated during the 

baking process and provides a condensation point for tars (POM); 

a baghouse is used to control fine particulate matter containing 

fluorides and POM. The dry alumina scrubber has been shown to 

achieve 99 to 99.6 percent control of TF emissions and 94 to 98 

percent control of POM emissions. For the bake furnace that is 
24 

not located at a primary aluminum plant, the MACT floor 

technology is an electrostatic precipitator. 

 2.4.4 Beyond MACT Floor Evaluation. The EPA's analysis of 

control options for new and existing sources revealed that the 

control technologies chosen to represent the MACT floor 

(described above) were the most efficient for the control of 

HAP's among the various control devices used in the industry. No 

additional control options were identified that had been 

demonstrated to be more effective than the MACT floor 

technologies at a reasonable cost or that would achieve 

significant additional reductions in HAP emissions. 

Consequently, the technologies associated with the MACT floor 

were also determined to represent the MACT technology. 

 

 For example, the retrofit of wet roof scrubbers was 

considered as a control option to reduce further the secondary 

emissions from the potlines. The analysis (see Appendix C) 

indicated that only a nominal additional emission reduction would 

be achieved on a nationwide basis by wet roof scrubbers at a very 

high additional cost. Consequently, wet roof scrubbers were 

determined not to represent the MACT control technology for 

potlines that do not have them based on consideration of 

nationwide impacts (such as the high cost relative to nominal 

reductions in emissions). The "beyond-the-floor" analysis 

focuses on the technology basis for determining MACT; it does not 

consider the potential effects on risk or other health 

considerations for a specific plant. Consequently, this analysis 

does not conclude that wet roof scrubbers are not applicable or 

reasonable for a specific plant if site-specific health 

considerations can be determined and are factored into the 

decision. However, an analysis of residual risk and the need to 

reduce it will be evaluated later (within 8 years of promulgation 

of the MACT standard). At that time, a consideration of health 

effects and potential reductions for a specific plant could 

indicate the wet roof scrubbers are warranted. 
25 

3.0 PROPOSED STANDARDS

 3.1 Emission Limits 

 Emission data from primary aluminum plants were solicited 

through two series of EPA information collection requests (ICR), 

from the industry trade association, from State agencies, and 

from individual plants. In addition, several primary aluminum 

plants were surveyed to collect additional detailed information 

on sources and processes. Emission tests also were conducted at 

seven plants as part of the MACT Test Program, which was funded 

jointly by EPA, the State of Washington Department of Ecology, 

and the industry. Additional emission test data also were 

submitted by individual plants. 

 The available data were evaluated to identify the "MACT" 

potrooms, anode bake furnaces, and paste production operations. 

The sampling and analytical procedures used historically by the 

plants were investigated and any differences from EPA procedures 

were evaluated. For each subcategory, the median potline was 

identified from the top 5 performing potlines to represent the 

performance associated with the MACT floor technology (i.e., the 

average emission limitation achieved by the top 5). Additional 

emission testing was performed for these potlines as needed to 

supplement the historical data, to characterize the emission 

control performance, and to obtain data on POM emissions. 

 Analysis of these available data leads EPA to conclude that 

the emission levels shown in Table 1 represent existing source 

MACT. These emission limits for potlines are in the same format 

as the NSPS (kg/Mg or lb/ton of aluminum). The proposed standard 

retains this format for anode bake furnaces, but uses lb/ton of 

anode rather than lb/ton aluminum equivalent as in the NSPS. 

 The limits for bake furnaces in Table 1 apply to bake 

furnaces located on the same site as the primary aluminum plant. 

 For the one bake furnace not located with a primary aluminum 

plant, the limits do not apply because the MACT control 

technology determined for the other bake furnaces (dry alumina 

scrubber) does not apply. However, the Louisiana Department of 

Environmental Quality has developed MACT standards for this plant 

under an approved State program. For this particular anode bake 

furnace plant, EPA is adopting the State's MACT determination. 

This approach is consistent with EPA's approach of working with 

the States, adopting MACT determinations from State programs when 

appropriate, and avoiding regulatory duplication. 

 For paste plants, the EPA concluded that it was not feasible 

to prescribe or enforce an emission standard; consequently, an 
26 

equipment standard was developed for this source [section 

112(h)]. The evaluation of the POM data for paste plants 
27 

 TABLE 1. SUMMARY OF PROPOSED EMISSION LIMITS 

 FOR EXISTING SOURCES 

 Source Emission Limit 

 Potlines TF Emission Limits 

0.95 kg/Mg (1.9 lb/ton) of aluminum 

produced for CWPB1a

 potlines 

1.5 kg/Mg (3.0 lb/ton) of aluminum 

produced for CWPB2a

 potlines 

1.25 kg/Mg (2.5 lb/ton) of aluminum produced for 

CWPB3a potlines 

0.80 kg/Mg (1.6 lb/ton) of aluminum 

produced for SWPBa

 potlines 

1.1 kg/Mg (2.2 lb/ton) of aluminum 

produced for VSS1a

 potlines 

1.35 kg/Mg (2.7 lb/ton) of aluminum 

produced for VSS2a

 potlines 

1.35 kg/Mg (2.7 lb/ton) of aluminum 

produced for HSSa

 potlines 

 POM Emission Limits 

2.35 kg/Mg (4.7 lb/ton) of aluminum 

produced for HSS potlines 

1.2 kg/Mg (2.4 lb/ton) of aluminum 

produced for VSS1 potlines 

1.85 kg/Mg (3.7 lb/ton) of aluminum 

produced for VSS2 potlines 
28 

 Paste 

 Production 

 POM Emission Limit 

Install, operate, and maintain 

equipment for capture of emissions 

and vent emissions to a dry coke 

scrubber. 

 Anode Bake 

Furnace 

(located 

with a 

primary 

aluminum 

plant) 

 TF Emission Limit 

0.10 kg/Mg (0.20 lb/ton) of anode 

 POM Emission Limit 

 0.09 kg/Mg (0.18 lb/ton) of anode 

a

 Abbreviations defined: 

CWPB1 =Center-worked prebake potline with the most modern 

reduction cells; includes all center-worked prebake

potlines not specifically identified as CWPB2 or CWPB3 

CWPB2 =Center-worked prebake potlines located at Alcoa in 

Rockdale, Texas; Kaiser Aluminum in Mead, Washington; 

Ormet Corporation in Hannibal, Ohio; Ravenswood 

Aluminum in Ravenswood, West Virginia; Reynolds Metals 

in Troutdale, Oregon; and Vanalco Aluminum in 

Vancouver, Washington 

CWPB3 =Center-worked prebake potline that produces very high 

purity aluminum, has wet scrubbers as the primary 

control system, and is located at the primary aluminum 

plant operated by NSA in Hawesville, Kentucky 

HSS =Horizontal stud Soderberg potline 

SWPB = Side-worked prebake potline 

VSS1 = Vertical stud Soderberg potline at Northwest Aluminum in 

The Dalles, Oregon, or at Columbia Aluminum in 

Goldendale, Washington 

VSS2 = Vertical stud Soderberg potlines at Columbia Falls 

Aluminum in Columbia Falls, Montana 
29 

concluded that it was not practical to set an emission limit 

because there were too few data to characterize the control 

performance that could be achieved by the various types of paste 

plants and because of uncertainty in the limited existing data. 

The high level of uncertainty would cause EPA to set a standard 

that could be impractical on a technological basis. The EPA 

considered drafting a standard that would require each owner or 

operator to conduct measurements to set limits on a case-by-case 

basis; however, the cost of this approach was not considered to 

be reasonable, especially given the reasonableness and 

effectiveness of specifying a design and equipment standard. 

Consequently, the proposed rule requires the installation of a 

capture system that collects and vents emissions to a dry coke 

scrubber (or equivalent alternative control device) for all paste 

production plants. If the owner or operator prefers to develop 

an applicable emission limit rather than comply with the 

equipment and design standard, this option is available under 

provisions for an alternative standard in section 112(h)(3). 

 In developing the emission limits, EPA considered different 

statistical approaches and different upper percentiles of 

performance. The industry generally recommended a level at least 

as high as the 99th percentile, and State representatives 

recommended using the 95th percentile. The EPA analyzed the data 

and considered the statistical approaches as well as examining 

the levels that had been achieved by the MACT floor plants. An 

important consideration in developing the proposed emission 

limits was that the monthly averages of the MACT floor potline 

must show that the limit has been achieved. 

 For cases with adequate historical data to determine the 

limit that had been achieved (e.g., TF from potlines), the MACT 

floor limits were determined from the highest monthly averages in 

the data base. In cases with no historical data (e.g., POM 

limits for all sources), the EPA used a statistical approach to 

estimate the MACT floor levels that had been achieved. 

Additional details on the data analysis are given in Appendix B, 

and a complete listing of the data is given in Appendix D. 

 Based on data submitted by the affected plant, EPA

determined that the CWPB3 potlines could have their wet primary 

control systems upgraded and improve control of secondary 

emissions to achieve a limit of 2.5 lb TF/ton as the MACT level 

of control, which has been the historic NSPS level for prebake 

potlines. Information supplied by NSA indicated that upgrading 

their wet scrubber system enabled them to meet a limit of 

2.5 lb TF/ton.17

 

 

 

17 Memorandum from W. Hill, Southwire Company, to M. McKeever, 

EPA:ESD, May 23, 1995. Docket Item II-D-85. 
30 

 The POM limits for HSS potlines were determined from the 

data collected during the MACT Test Program. The 95th percentile 

was used to determine the POM limit for the HSS subcategory for 

both the primary control system and secondary emissions. The POM 

limits for VSS1 are based on the limited test data available from 

one potline at Columbia-Goldendale and one potline at Northwest 

Aluminum. The results from these two potlines were combined to 

provide enough data to assess performance and to represent the 

MACT floor. These two potlines achieved a level of 2.4 lb/ton. 

There were no validated POM data available for the VSS2 

subcategory; however, POM data for the VSS1 subcategory before 

the wet roof scrubbers represent the same process configuration 

as that for VSS2. Consequently, the VSS1 POM data were used to 

derive limits for VSS2. The POM emissions at the inlet to the 

wet roof scrubbers did not exceed 3.7 lb/ton. Additional details 

are provided in Appendix B and Appendix D. 

 For anode bake furnaces located at primary aluminum plants, 

POM limits were developed from the two best performing furnaces 

in the industry with the MACT technology (dry alumina scrubbers), 

which were the only ones for which EPA had adequate data to 

determine the MACT level of control. The emission limit for TF 

from anode bake furnaces was based on data from Noranda's bake 

furnace, which supported a level equal to the NSPS level of 

control. Eight bake furnaces currently are subject to the NSPS, 

and the NSPS level has been achieved by an older bake furnace 

that is not subject to the NSPS. 

 Emission limits are also proposed for new and reconstructed 

potlines and anode bake furnaces. [See Table 2.] These emission 

limits are based on data from the best controlled potline and 

bake furnace. An equipment standard (dry coke scrubber) is 

proposed for new paste plants. MACT for new sources applies to 

all new and reconstructed potlines, and no distinction is made 

for the different subcategories that were developed for existing 

potlines. As provided in the definition of "reconstruction" in 

the proposed rule, two criteria must be met for a source to be 

considered reconstructed and subject to new source MACT: (1) all 

of the major components of the source must be replaced (for 

example, the major components of a potline include the raw 

material handling system, reduction cells, superstructure, 

hooding, ductwork, etc.), and (2) it must be technically and 

economically feasible for the reconstructed source to meet new 

source MACT. 

 The EPA believes that it is unlikely that an existing 

potline could be reconstructed in such a manner that it would be 

technically feasible for the potline to meet new source MACT 

unless the criteria described above are met. For example, the 

conversion of a Soderberg potline to a prebake potline, while 
31 

retaining some of the major components of the original potline, 

is expected to subject the source to emission limits for existing 

prebake potlines rather than triggering new source MACT. 

Similarly, if an existing potline is modified to increase 

capacity (e.g., by adding more reduction cells), the modified 

potline would continue to be subject to MACT for existing 

sources. 

 Another example is the conversion of a SWPB potline to a 

CWPB potline, which is not expected to be a reconstruction if 

some of the major components of the original potline are 

retained. However, when an existing potline is changed in such a 

manner that the applicable subcategory changes, the changed 

potline must meet the applicable limit for the original 

subcategory or the applicable limit for the new subcategory, 

whichever is more stringent. In other words, an existing potline 

cannot qualify for less stringent emission limits associated with 

another subcategory as a result of changes to its operation. 

 TABLE 2. SUMMARY OF PROPOSED EMISSION LIMITS FOR NEW SOURCES 

 Source Emission Limit 

 Potlines 

 

 TF Emission Limit 

 0.6 kg/Mg (1.2 lb/ton) of aluminum produced 

 

 POM Emission Limit 

0.32 kg/Mg (0.63 lb/ton) of aluminum produced 

 Paste 

 Production 

 POM Emission Limit 

Install and operate equipment for the capture 

of emissions and vent emissions to a dry 

coke scrubber 

 Anode Bake 

 Furnace 

 TF Emission Limit 

 0.01 kg/Mg (0.02 lb/ton) of anode 

 POM Emission Limit 

 0.025 kg/Mg (0.05 lb/ton) of anode 
32 

3.2 Monitoring and Compliance Requirements

 The EPA identified and analyzed several different options 

for enhanced monitoring of primary and secondary emissions from 

new and existing plants. The major HAPs of interest from the 

primary aluminum industry include HF and POM. Currently, there 

is no known continuous emission monitor (CEM) for POM; however, 

devices are available for the continuous monitoring of HF 

emissions. These devices can be used to monitor both primary and 

secondary HF emissions from the potlines and for HF emissions 

from the anode bake furnace. A continuous opacity monitor also 

could be used for visible emission observations to ensure proper 

operation of the control system. 

 Most plants currently perform emission tests as often as 

once to three times per month for pollutants such as particulate 

matter (PM) and TF. Currently, very little sampling and testing 

is performed for POM emissions. Methods 13 and 14 can be used to 

determine the quantity of TF from aluminum production. The 

analysis adds particulate and gaseous fluoride (GF) captured in 

the front half filter to GF from the back-half impingers to 

determine total fluoride. In addition, a method has been 

developed to provide a surrogate measure of POM emissions 

(Method 315). This method uses a gravimetric determination of 

methylene chloride extractables from both the front and back 

halves of the sampling train. Methylene chloride extracts that 

portion of the particulate matter that is POM; however, it is a 

surrogate because it also extracts some material that is not POM. 

 Options for manual sampling include sampling at different 

frequencies; manual sampling for each potline; or sampling one 

potline to represent a group of similar potlines. 

 Parametric monitoring also is an option and includes 

monitoring of certain parameters associated with the production 

process, the control device, or both to ensure proper operation 

of the control system. These parameters may be monitored on a 

more frequent basis than periodic manual sampling to supplement 

the manual sampling. Examples of possible monitoring parameters 

for a dry alumina scrubber include the alumina flow rate, air 

flow rate, pressure drop, and inlet gas temperature. For a wet 

scrubber and secondary emissions, parameters could include the 

scrubbing liquor flow rate, the pressure drop across the 

scrubber, and air flow. Parameters for secondary emissions also 

could include inspections to observe work practices; the 

condition of the hoods and shields; the number of shields 

removed; the frequency of removal, and the duration. Visual 

observations of opacity, a bag break detection system, and 

periodic inspection of fabric filters for tears or gaps also 

could be made. 
33 

 The EPA considered the various options for monitoring and 

concluded that the provisions selected for proposal (see Table 3) 
34 

 TABLE 3. PROPOSED MONITORING AND COMPLIANCE REQUIREMENTS 

 Source Requirement 

Potlines 1.Monthly sampling for TF secondary emissions 

from each potline plus quarterly POM 

sampling for Soderberg potlines. May 

sample one potline to represent a similar 

potline(s). 

2.If one potline represents one or more similar 

potlines, the owner or operator must 

monitor the similar potline(s) with an HF 

CEM or an Alcan cassette sampler. These 

devices must meet certain Method 14 

criteria, and an enforceable limit for 

these devices must be established based on 

simultaneous performance testing using 

Methods 13 and 14. 

3.An HF CEM or Alcan cassette sampler can be 

used instead of manual sampling if the 

owner or operator correlates or 

demonstrates them to be equivalent to 

Methods 13 and 14 to the satisfaction of 

the regulatory authority. 

4.Annual sampling of TF and POM (for Soderberg 

potlines only) from each primary control 

system. 

5.Monitor control device parameters. 

6.Install monitoring device to measure weight of 

aluminum produced. 

7.Compute a monthly average from at least 3 runs 

for secondary emissions and the 12-month 

average of tests of the primary control 

system (at least 3 runs per year). Using 

the monthly average and 30-day average 

production rate, compute TF emissions in 

lb/ton to determine compliance. POM 

emissions are determined in a similar 

manner (for Soderbergs only) on a quarterly 

basis from at least one run for secondary 

emissions per month and 3 runs annually for 

emissions from the primary control system. 
35 

 Source Requirement 

 Paste 

 Production 

1.Install required equipment. 

 

2.Monitor process parameters for control device. 

 Anode Bake 

 Furnace 

1.Monitor process parameters for control device. 

2.Install monitoring device for weight of green 

anodes placed in the bake furnace. 

3.Annual sampling for TF and POM from furnace 

stack. Compute average of at least 3 runs 

and weight of anodes to determine 

compliance. 
36 

represented a cost-effective approach to determine emission 

control performance. Periodic manual sampling was chosen to 

measure emissions instead of an HF CEM because CEMs have not been 

adequately demonstrated and validated. However, the EPA 

encourages the development and future use of HF CEMs for 

secondary emissions because they show promise for improved 

measurement of HF emissions and as a tool for improved process 

control. In addition to periodic manual sampling, monitoring of 

control device parameters is proposed to ensure that the control 

device is operated properly on a continuous basis. Additional 

details on the monitoring requirements are given in the following 

sections; highlights are given in Table 3. 

 3.2.1 Potlines. The proposed rule would require compliance 

monitoring for each new and existing potline (or similar 

potline). For secondary emissions of TF from each potline (or 

group of similar potlines) exiting the roof monitor, the proposed 

rule would require the owner or operator to perform at least 

three runs each month by Methods 13 and 14. If wet roof 

scrubbers are used, the owner or operator would measure emissions 

using methods approved by the regulatory authority. For POM 

emissions from Soderberg potlines, the owner or operator would 

perform one run per month (three runs per quarter) using a Method 

14 sampling manifold and procedures and Method 315 (proposed as 

part of this rulemaking) for POM analyses. 

 Plants may sample secondary emissions from one potline to 

represent similar potlines rather than perform manual sampling on 

each potline. To show that a potline is similar, the owner or 

operator must demonstrate (to the satisfaction of the regulatory 

authority) that the level of emission control is the same for all 

of the potlines in the group. An HF CEM or Alcan cassette 

sampler may be used to demonstrate compliance by similar potlines 

that are not manually sampled. An emission limit for the device 

must be established based on a minimum of 9 simultaneous runs 

using Methods 13/14 and the alternative monitoring device. The 

alternative limit may be based on a mathematical correlation of 

the results and the applicable TF limit or it may be based on the 

highest reading of the alternative device that corresponds to a 

Method 13/14 result that is in compliance with the applicable TF 

limit. The similar potline must be monitored with the HF CEM or 

Alcan cassette on the same frequency as that required for manual 

sampling. Exceeding the emission limit established for the 

alternative device would be a violation. Procedures are also 

included to develop alternative methods for POM determinations. 

 The industry has requested and EPA is considering work 

practice inspections as a monitoring alternative to show similar 

levels of control for similar potlines. This approach may be 

feasible. However, this issue is unresolved because every 
37 

specific work practice and its corresponding effect on emissions 

are difficult to identify and quantify, and there is no evidence 

that a work practice "score" is relatable to emission rates. 

Consequently, there have been difficulties in developing work 

practice inspections as an acceptable alternative compliance 

approach. 

 Methods other than manual sampling using Methods 13 and 14 

may be approved on a case-by-case basis by the regulatory 

authority. The EPA is encouraging the development and use of HF 

CEMs to monitor secondary emissions because they show promise for 

improved monitoring, lower costs, and better process control of 

fluoride losses. Alternative methods must be correlated with 

Method 13 and 14 results to the satisfaction of the regulatory 

authority. Alternative methods must account for or include 

gaseous fluoride and cannot be based on measurement of 

particulate matter or particulate fluoride alone because HF, the 

HAP of interest, is in gaseous form. For example, the use of the 

Alcan cassette has been approved for TF measurements at one plant 

in the CWPB1 subcategory based on a demonstrated correlation to 

the results from Method 14. Demonstrations would be required to 

obtain approval to use the Alcan cassette for potlines in other 

subcategories (such as the Soderberg subcategories) because of 

potential differences in emission characteristics, including the 

effects of higher levels of particulate matter. 

 For the primary control system, the proposed rule would 

require the owner or operator to sample each primary control 

device on an annual basis (at minimum) for TF emissions using 

Method 13 and for POM (from Soderberg potlines only) using 

Method 315. For both the TF and the POM tests, at least three 

runs are required. If there are multiple primary control devices 

or stacks, the owner or operator must rotate sampling or sample 

representative stacks to ensure that each primary control device 

is sampled during the year (i.e., at least one run per control 

device). If the primary control system is tested more than once 

during the previous 12-month period, the average of all runs for 

the 12-month period is used to determine the contribution from 

the primary control device. 

 The owner or operator also would install, operate, and 

maintain a device for the monitoring and recording of process 

parameters to ensure proper operation of the control system. For 

dry alumina scrubbers, the devices must monitor and record the 

alumina flow and the air flow of the device. For wet scrubbers 

used as primary control devices, the device must monitor and 

record the water flow rate to the scrubber and the air flow rate. 

 Plants using electrostatic precipitators must install devices to 

monitor voltage and secondary current. In addition, the stacks 

of all primary control systems must be visually inspected each 
38 

day for indication of abnormal operation. Plants with wet roof 

scrubbers that control secondary emissions must monitor total 

water flow and inspect each scrubber each day to ensure each one 

is operating properly. If an emission control device other than 

one of those described above is used, the owner or operator must 

include recommended monitoring parameters in the part 70 permit 

application. 

 Using data from the initial performance test and historical 

performance tests, the owner or operator would use these 

monitoring devices to determine the upper and/or lower operating 

limits, as appropriate, for each parameter. The owner or 

operator may redetermine the upper and/or lower operating limits, 

as appropriate, based on historical data or other information and 

submit an application to the regulatory authority to change the 

applicable limits. 

 The monitoring parameter limit(s) would be used as the 

baseline against which subsequent readings would be compared to 

ensure normal operation of the control device. A corrective 

action program would be triggered if the control device is 

operating outside of the acceptable range for the specified 

parameters. Failure to initiate corrective actions within one 

hour after exceeding the limit is a violation. A violation also 

occurs if the operating limit for a parameter is exceeded more 

than 6 times in any semiannual reporting period. For the purpose 

of determining the number of exceedances, no more than one 

exceedance would be attributed in any given 24-hour period. The 

EPA limited the number of times the monitoring parameter(s) could 

be exceeded without a violation (no more than 6 times in a 

semiannual period) to ensure that the control equipment is 

properly repaired under the corrective action program. The 

semiannual period also provides the owner or operator adequate 

time to submit a request to redetermine the limit(s) as described 

earlier if historical data or other information shows that the 

original monitoring parameter limits are no longer appropriate. 

 To determine compliance with the single emission limit for 

primary and secondary emissions from the potline, the plant owner 

or operator would compute the monthly average (minimum of three 

runs per month) for secondary emissions of TF and quarterly 

emissions of POM (from a minimum of one run per month for 

Soderberg potlines) from each potline. Using the emission test 

results (the average of at least 3 runs for secondary emissions 

and the most recent annual test or 12-month average of the 

primary control system) and the 30-day average production rate 

for aluminum production, the owner or operator would calculate 

the emissions in a kg/Mg (lb/ton) format to compare to the 

emission limits in the rule. The results of the secondary 

emission tests and the most recent compliance test for the 

primary control system are added together and compared to the 
39 

emission limit. If the average value is less than the applicable 

emission limit, the potline (or group of similar potlines) is in 

compliance. 

 Compliance with the standard must be demonstrated at startup 

for new sources and within 2 to 3 years of the effective date of 

the final rule for existing sources, depending on the changes 

needed at a given plant to meet the standards. All plants have 

at least 2 years to comply. Plants that demonstrate that more 

time is needed to install control equipment for a specific source 

will be given three years to comply for that source. The owner 

or operator must submit semiannual reports of excess emissions 

and semiannual reports of startups, shutdowns, and malfunctions 

(if applicable). 

 3.2.2 Anode Bake Furnaces. The proposed rule would require 

the owner or operator to sample TF emissions from new and 

existing anode bake furnaces using Method 13 and to sample POM 

emissions using Method 315. Both pollutants must be sampled 

annually; at least three runs must be performed. The provisions 

for establishing monitoring parameter limits, monitoring of 

control device parameters, corrective actions, etc. are the same 

as those described earlier for potlines. 

 3.2.3 Paste Production. The proposed rule would require 

the owner or operator to install and operate a capture system 

vented to a dry coke scrubber (or equivalent alternative control 

device) for new and existing paste plants. There were only 

limited data18,19 available to characterize the performance of dry 

coke scrubbers, and after review of the data, the EPA determined 

that a control efficiency of 90 percent was achievable for batch 

mixers and 95 percent was achievable for continuous mixers. 

Consequently, if a control device other than a dry coke scrubber 

is used, the proposed rule requires that the alternative control 

 achieve a POM reduction efficiency of at least 95 percent for 

continuous paste mixing operations and at least 90 percent for 

batch operations. In addition, the owner or operator must 

install, calibrate, maintain, and operate a monitoring device to 

measure and record the coke flow rate and the air flow rate to 

the scrubber (or other parameters for an approved alternative 

device). If other control devices are used, the owner or 

operator must include recommended monitoring parameters in the 

part 70 permit application. The provisions for monitoring of 

 

 

18 Emissions Measurements Test Report - Northwest Aluminum 

Company. Prepared by Entropy, Inc. June 1994. 77 p. 

 

19 Kaiser Aluminum and Chemical Corporation Method 5/POM and 

13B Testing - Mead, Washington - March 15-24, 1994. Prepared by 

AmTest Air Quality, Inc. November 9, 1994. pp. 1 to 99. 
40 

control device parameters, corrective actions, etc. are the same 

as those described earlier for potlines. 

 

 3.2.4 Emission Averaging. The proposed rule contains 

provisions for the averaging of TF emissions from potlines and 

anode bake furnaces. Emission sources not located on the plant 

site or not within the same State or permitting jurisdiction 

would not be eligible for emissions averaging and averaging would 

be limited to TF emissions from like sources. For example, TF 

emissions from one potline can be averaged with the TF emissions 

from another potline at the same plant. Each emission point used 

in emission averaging must be sampled to ensure an accurate 

accounting of emissions. Averaging would not be allowed between 

two different pollutants (e.g., TF and POM). Emissions averaging 

would not be allowed in any State that selects to exclude this 

option from their operating permits program under the provisions 

of the proposed rule. To conduct the emissions averaging, the 

owner or operator would include an Averaging Plan in their part 

70 permit application identifying each potline or group of 

potlines in the average, and the assigned TF emission limit for 

each potline or similar potline. 

 The option that was developed for emission averaging is a 

monthly average for TF and a quarterly average for POM for the 

group of sources that ensures emissions are less than the level 

achieved by the limit for individual sources. The limit for 

averaging is lower than the limit for individual sources and was 

calculated by estimating the decrease in standard deviation 

(variability) when multiple potlines are included in the average. 

 The applicable emission limits for emissions averaging for the 

possible combinations of sources at existing plants are given in 

Table 4. The emission limits decrease as the number of sources 

included in the average increases because of the lower 

variability when more sources are included. Additional details 

on the derivation of emission limits for emissions averaging are 

given in Appendix B. 

 For plants choosing to use emission averaging, at least 

three runs must be made each month for TF for secondary emissions 

from each potline to determine the average emissions from each 

potline. The sum of emissions from each potline (including both 

the primary system and secondary emissions) for the month is 

divided by the total aluminum production from all of the potlines 

for the month to determine the monthly emissions in lb/ton for 

comparison to the limit. The approach is the same for POM from 

Soderberg potlines except that three runs are made each quarter 

(one run per month) instead of three runs each month. 

 Options were also developed for emissions averaging for POM 

using the same basic procedure described for TF. The proposed 

limits for POM for emissions averaging are also given in Table 4. 
41 

 Emissions averaging limits were also developed for bake 

furnaces for plants with multiple furnaces that must be sampled 

annually and are presented in Table 5. The limits for TF were 

based on the results for Noranda's bake furnace and the limits 

for POM were developed from the tests of the Kaiser-Mead bake 

furnace. The same procedures used for developing limits for 

potlines were used for bake furnaces and are described in 

Appendix B. 
42 

 TABLE 4. POTLINE TF AND POM LIMITS FOR EMISSIONS AVERAGING

Type Monthly TF limit (lb/ton) for given number of potlines

 2 lines 3 lines 4 lines 5 lines 6 lines 7 lines 8 lines 

CWPB1 1.7 1.6 1.5 1.5 1.4 1.4 1.4 

CWPB2 2.9 2.8 2.7 2.7 2.6 2.6 2.6 

CWPB3 2.3 2.2 2.2 2.1 2.1 2.1 2.1 

VSS1 2.0 1.9 1.8 1.7 1.7 1.7 1.7 

VSS2 2.6 2.5 2.5 2.4 2.4 2.4 2.4 

HSS 2.5 2.4 2.4 2.3 2.3 2.3 2.3 

SWPB 1.4 1.3 1.3 1.2 1.2 1.2 1.2 

 Quarterly POM limit (lb/ton) for number of potlines

HSS 4.1 3.8 3.7 3.5 3.5 3.4 3.3 

VSS1 2.1 2.0 1.9 1.9 1.8 1.8 1.8 

VSS2 3.4 3.2 3.2 3.1 3.1 3.0 3.0 
43 

 TABLE 5. BAKE FURNACE EMISSION LIMITS FOR EMISSIONS AVERAGING

Number of 

furnaces 

Limit (lb/ton of anode) 

 TF POM 

2 0.11 0.17 

3 0.090 0.17 

4 0.077 0.17 

5 0.070 0.17 

 The owner or operator may submit an application to the 

regulatory authority to revise their averaging plan. In 

addition, owners or operators who do not choose to use emission 

averaging for initial compliance may submit a request to 

implement averaging after the initial compliance date. 

 3.2.5 Reduced Sampling Frequency. The proposed rule also 

contains provisions for reduced sampling frequency for both TF 

and POM. The owner or operator may petition the regulatory 

authority to establish an alternative testing requirement that 

requires less frequent testing for secondary emissions, the 

primary control system, or the anode bake plant. If the owner or 

operator shows that the emissions from these sources have low 

variability during normal operations, the regulatory authority 

may establish an alternative testing requirement. The 

alternative testing requirement must include a testing schedule 

and the method to be used to measure emissions for the purpose of 

performance tests. 

 Guidance is provided to the owner or operator and the 

regulatory authority for evaluating alternative sampling 

frequencies in the EPA report, Primary Aluminum: Statistical 

Analysis of Potline Fluoride Emissions and Alternate Sampling 

Frequency (EPA-450/3-86-012, October 1986). Plants that have 

received approval for an alternate sampling frequency under the 

NSPS may continue this alternate frequency under the proposed 

NESHAP. 
44 

3.3 Recordkeeping and Reporting Requirements 

 The proposed standards would incorporate nearly all 

notification, recordkeeping, and reporting requirements in the 

General Provisions to Part 63. These include: (1) initial 

notifications, notification of performance test, notification of 

compliance status, and (2) a report of performance test results, 

semiannual report of startup, shutdown, and malfunctions (if 

applicable), and semiannual reports of excess emissions. The 

General Provisions also require the owner or operator to develop 

a startup, shutdown, and malfunction plan. Table 6 shows the 

recordkeeping and reporting requirements in the General 

Provisions and the applicability of these requirements to the 

requirements in the proposed rule. 

 In addition to the records required by the General 

Provisions to part 63, the proposed rule would require new and 

existing aluminum plants to maintain records of daily production 

rates for aluminum and anodes. This information is needed to 

document the 30-day average production rate used in compliance 

equations. The proposed standard also would require the owner or 

operator choosing to use emission averaging as a means of 

compliance to develop and submit an Averaging Plan to the 

applicable regulatory authority, who would review and approve or 

disapprove the plan based on specified criteria within a 

specified time frame. 

 3.4 Delegation of Authority

 Following promulgation, EPA will delegate authority to 

States to implement and enforce the rule. As proposed, the rule 

includes provisions allowing States to choose whether to include 

provisions for emission averaging in their program and in permits 

issued under their program. 
45 

 TABLE 6. APPLICABILITY OF GENERAL PROVISIONS 

 (40 CFR Part 63, Subpart A) TO SUBPART LL 

 General Provisions 

 Citation 

 Requirement Applies to 

Subpart LL 

 Comment 

63.1(a)(1) Applicability Yes 

63.1(a)(2) Yes 

63.1(a)(3) Yes 

63.1(a)(4) Yes 

63.1(a)(5) No [Reserved] 

63.1(a)(6)-(a)(8) Yes 

63.1(a)(9) No [Reserved] 

63.1(a)(10) Yes 

63.1(a)(11) Yes 

63.1(a)(12)-(a)(14) Yes 

63.1(b)(1) Yes 

63.1(b)(2) Yes 

63.1(b)(3) Yes 

63.1(c)(1) Applicability 

After Standard 

Established 

Yes 

63.1(c)(2) No All are major 

sources 

63.1(c)(3) No [Reserved] 

63.1(c)(4) Yes 

63.1(c)(5) Yes 

63.1(d) No [Reserved] 

63.1(e) Applicability 

of Permit 

Program 

Yes 

63.2 Definition of 

"Reconstruction" 

No Defined in 

Subpart LL 

63.2 All Other 

Definitions 

Yes Additional 

definitions 
46 

 General Provisions 

 Citation 

 Requirement Applies to 

Subpart LL 

 Comment 

in § 63.841 

63.3(a)-(c) Units and 

Abbreviations 

Yes 

63.4(a)(1)-(a)(3) Prohibited 

Activities 

Yes 

63.4(a)(4) No [Reserved] 

63.4(a)(5) Yes 

63.4(b)-(c) Yes 

63.5(a)(1) Construction/ 

Reconstruction 

Yes 

63.5(a)(2) Yes 

63.5(b)(1) Existing, New, 

Reconstructed 

Yes 

63.5(b)(2) No [Reserved] 

63.5(b)(3) Yes 

63.5(b)(4) Yes 

63.5(b)(5) Yes 

63.5(b)(6) Yes 

63.5(c) No [Reserved] 

63.5(d)(1) Approval of 

Construction/ 

Reconstruction 

Yes 

63.5(d)(2) Yes 

63.5(d)(3) Yes 

63.5(d)(4) Yes 

63.5(e) Yes 

63.5(f)(1) Yes 

63.5(f)(2) Yes 

63.6(a) Compliance for 

Standards and 

Maintenance 

Yes 
47 

 General Provisions 

 Citation 

 Requirement Applies to 

Subpart LL 

 Comment 

63.6(b)(1) Yes 

63.6(b)(2) Yes 

63.6(b)(3) Yes 

63.6(b)(4) Yes 

63.6(b)(5) Yes 

63.6(b)(6) No [Reserved] 

63.6(b)(7) Yes 

63.6(c)(1) Compliance 

Date for 

Existing 

Sources 

No Subpart LL 

specifies 

compliance 

date for 

existing 

sources 

63.6(c)(2) Yes 

63.6(c)(3)-(c)(4) No [Reserved] 

63.6(c)(5) Yes 

63.6(d) No [Reserved] 

63.6(e)(1)-(e)(2) Operation & 

Maintenance 

Yes 

63.6(e)(3) Startup, 

Shutdown 

Malfunction 

Plan 

Yes 

63.6(f)(1) Compliance 

with Emission 

Standards 

Yes 

63.6(f)(2) Yes 

63.6(f)(3) Yes 

63.6(g)(1)-(g)(3) Alternative 

Standard 

Yes 

63.6(h) Opacity/VE 

Standards 

No Subpart LL 

does not 

require COMS, 
48 

 General Provisions 

 Citation 

 Requirement Applies to 

Subpart LL 

 Comment 

VE or opacity 

standards 

63.6(i)(1)-(i)(14) Extension of 

Compliance 

Yes 

63.6(i)(15) No [Reserved] 

63.6(i)(16) Yes 

63.6(j) Exemption from 

Compliance 

Yes 

63.7(a)(1)-(a)(3) Performance 

Testing 

Requirements 

Yes 

63.7(b) Notification Yes 

63.7(c) Quality 

Assurance/Test 

Plan 

Yes 

63.7(d) Testing 

Facilities 

Yes 

63.7(e)(1) Conduct of 

Tests 

Yes 

63.7(e)(2) Yes 

63.7(e)(3) Yes 

63.7(e)(4) Yes 

63.7(f) Alternative 

Test Method 

Yes 

63.7(g) Data Analysis Yes 

63.7(h) Waiver of 

Tests 

Yes 

63.8(a)(1) Monitoring 

Requirements 

Yes 

63.8(a)(2) Yes 

63.8(a)(3) No [Reserved] 

63.8(a)(4) Yes 

63.8(b)(1) Conduct of Yes 
49 

 General Provisions 

 Citation 

 Requirement Applies to 

Subpart LL 

 Comment 

Monitoring 

63.8(b)(2) Yes 

63.8(b)(3) Yes 

63.8(c)(1) CMS Operation/ 

Maintenance 

Yes 

63.8(c)(2) Yes 

63.8(c)(3) Yes 

63.8(c)(4) - (c)(8) CMS Operation/ 

Maintenance 

No Subpart LL 

does not 

require 

COMS/CMS or 

CMS 

performance 

specification 

63.8(d) Quality 

Control 

No 

63.8(e) Performance 

Evaluation for 

CMS 

No 

63.8(f)(1)-(f)(5) Alternative 

Monitoring 

Method 

Yes 

63.8(f)(6) Alternative to 

RATA Test 

Yes 

63.8(g) Data Reduction Yes 

63.9(a) Notification 

Requirements 

Yes 

63.9(b)(1) Initial 

Notifications 

Yes 

63.9(b)(2) Yes 

63.9(b)(3) Yes 

63.9(b)(4) Yes 

63.9(b)(5) Yes 

63.9(c) Request for 

Compliance 

Yes 
50 

 General Provisions 

 Citation 

 Requirement Applies to 

Subpart LL 

 Comment 

Extension 

63.9(d) New Source 

Notification 

for Special 

Compliance 

Requirements 

Yes 

63.9(e) Notification 

of Performance 

Test 

Yes 

63.9(f) Notification 

of VE/Opacity 

Test 

No 

63.9(g) Additional CMS 

Notifications 

No Subpart LL 

does not 

include 

VE/opacity 

standard 

63.9(h)(1)-(h)(3) Notification 

of Compliance 

Status 

Yes 

63.9(h)(4) No [Reserved] 

63.9(h)(5)-(h)(6) Yes 

63.9(i) Adjustment of 

Deadlines 

Yes 

63.9(j) Change in 

Previous Info. 

Yes 

63.10(a) Recordkeeping/ 

Reporting 

Yes 

63.10(b) General 

Requirements 

Yes 

63.10(c)(1) Additional CMS 

Recordkeeping 

Yes 

63.10(c)(2)-(c)(4) No [Reserved] 

63.10(c)(5)-(c)(6) Yes 

63.10(c)(7)-(c)(8) Yes 
51 

 General Provisions 

 Citation 

 Requirement Applies to 

Subpart LL 

 Comment 

63.10(c)(9) No [Reserved] 

63.10(c)(10)-(11) Yes 

63.10(c)(12)-(14) Yes 

63.10(c)(15) Yes 

63.10(d)(1) General 

Reporting 

Requirements 

Yes 

63.10(d)(2) Performance 

Test Results 

Yes 

63.10(d)(3) Opacity or VE 

Observations 

No Subpart LL 

does not 

require COM 

or limits for 

VE/opacity 

63.10(d)(4) Yes 

63.10(d)(5) Startup, 

Shutdown, 

Malfunction 

Reports 

Yes 

63.10(e)(1) Additional CMS 

Reports 

Yes 

63.10(e)(2) Reporting 

Performance 

Evaluations 

No Performance 

evaluation 

not required 

63.10(e)(3) Excess 

Emissions and 

CMS Performance Reports 

Yes Exceedances 

of parameter 

limits are 

excess 

emissions 

63.10(f) Waiver for 

Recordkeeping/ 

Reporting 

Yes 

63.11(a)-(b) Control Device 

Requirements 

No Flares not 

applicable 

63.12(a)-(c) State 

Authority and 

Delegations 

Yes 
52 

 General Provisions 

 Citation 

 Requirement Applies to 

Subpart LL 

 Comment 

63.13(a)-(c) State/Regional 

Addresses 

Yes 

63.14(a)-(b) Incorporation 

by Reference 

Yes 

63.15(a)-(b) Availability 

of Information 

Yes 

4.0 SUMMARY OF ENVIRONMENTAL, COST, ENERGY, AND ECONOMIC IMPACTS

 Currently, there are 23 primary aluminum plants, owned by 11 

companies, are located in 14 States. The EPA estimates of the 23 

plants, 19 would need to upgrade controls on at least one process 

to reduce emissions. All plants would be subject to the 

recordkeeping and reporting requirements. 

 4.1 Air Quality Impacts

 Nationwide emissions from primary aluminum production 

operations are estimated at 6,400 tpy of TF. After

implementation of the proposed standards, these emissions would 

decrease by almost 50 percent, to 3,400 tpy. POM emissions would 

be reduced by about 45 percent, from 3,200 tpy to 1,800 tpy. TF 

emissions from the anode bake furnaces are estimated at 700 tpy; 

POM emissions are estimated at 555 tpy. After control of all 

bake furnaces, TF emissions would be reduced by 97 percent and an 

84-percent reduction would be achieved for POM emissions. POM 

emissions from paste production plants, estimated at 147 tpy at 

baseline, would be reduced by about 130 tpy, to about 16 tpy -- 

an 89-percent reduction from current levels. Emissions of other 

HAP included in the TF and POM emissions would also be reduced, 

as would nonHAP pollutants such as PM. For example, PM emissions 

would be reduced by 16,000 tpy. 

 

 4.2 Solid Waste Impacts

 Solid waste is generated by wet air emission control 

devices, such as wet scrubbers and wet ESPs, and the accompanying 

wastewater treatment. Dry alumina scrubbing techniques do not 

generate any solid wastes because all captured solids are 

returned to the process. Wet scrubbers and wet ESPs generate 

from 6,000 to 15,000 tpy of solid waste, depending on the size of 

the plant. When dry scrubbers are used and all the captured 

solids are returned to the process, solid waste generation could 

be reduced by 6,000 to 15,000 tpy for a typical plant. None of 

the other control options has a significant impact on the 

generation of solid waste. 
53 

 4.3 Cost Impacts 

 The estimated nationwide capital and annual costs of the 

proposed standards for all sources is $160 million and $40 

million per year, respectively. The major components of the 

total costs are the control costs for potlines, which are 

estimated as $104 million in capital with a total annual cost of 

$23 million per year. The major cost impacts expected arise from 

the installation of dry alumina scrubbers for the primary control 

system at one plant and work practices, operating procedures, 

maintenance and repair, and equipment modifications at most 

plants. A few plants may incur capital costs to upgrade wet 

scrubbers used for primary control, to replace or upgrade hoods 

or doors, and to install automated equipment for improved 

emission control. 

 The cost estimates for paste production assume that the 18 

plants without dry coke scrubbers for the control of POM 

emissions will install one. However, some plants may be able to 

meet the proposed performance standard with dry alumina scrubbers 

or other control devices, or they may be able to utilize many of 

the components of their existing system. The total capital cost 

is estimated at $26 million and the estimated total annualized 

cost is $6.1 million per year. 

 A dry alumina scrubber system similar to that used for the 

aluminum production process removes fluoride, POM, and fine 

particulate from the anode baking furnace exhaust gases. The 

system consists of a dry alumina fluidized bed scrubber, a 

baghouse, and the associated duct work and fans to collect and 

move the gases from the furnace. The scrubber adsorbs fluorides 

and POM, which are removed with other particulate matter in the 

baghouse. The spent alumina is then recycled to the potlines and 

the cleaned gases are released through a stack. The total 

capital cost, estimated at $20.6 million, assumes that all plants 

without a dry alumina scrubber (5 of 17) must install one. The 

total annualized cost is estimated at $6.2 million per year. 

 The direct operating costs for paste production and anode 

bake furnaces were estimated by averaging the operating costs for 

the dry coke or dry alumina scrubbers that were reported by the 

industry in survey responses. The operating costs reported by 

the industry were converted into 1994 dollars and resulted in an 

annual direct operating cost of $1.16 per ton of paste and $4.81 

per ton of anode. 

 The EPA examined several options for enhanced monitoring, 

ranging from requiring the use of the HF continuous emission 

monitor to requiring monitoring of process parameters with annual 
54 

emission tests. The EPA, in conjunction with States and industry 

representatives, selected monthly monitoring of secondary TF 

emissions, quarterly sampling on secondary POM emissions, and 

annual sampling of controlled primary emissions, coupled with 

monitoring of process parameters, as the most reasonable approach 

consistent with current State practices. 

 Currently, about one-third of existing potlines are sampled 

for TF on a regular basis. Because of the flexibility provided 

in the rule, many plants are expected to take advantage of the 

use of HF CEMs and Alcan cassettes for similar potlines, both of 

which are much less expensive than manual sampling using 

Methods 13 and 14. The nationwide capital cost estimate of 

$7 million for monitoring equipment includes new Method 14 

manifolds, HF CEMs, and Alcan cassettes. The total annualized 

cost of monitoring is estimated as about $4 million per year once 

all plants comply with the rule. These costs may be reduced 

significantly as plants qualify for reduced sampling frequency 

(e.g., quarterly instead of monthly). The CEM will have value as 

a process monitoring tool, in addition to its use for monitoring 

to determine compliance. 

 4.4 Economic Impacts

 The goal of the economic impact analysis was to estimate the 

market response to the proposed rule and determine whether there 

would be adverse impacts associated with it. To assess the 

industry-wide impacts of control costs, the market price increase 

resulting from the proposed rule was estimated for the primary 

aluminum industry. The market price increase estimate was 

derived by aggregating the control costs for all existing primary 

aluminum facilities and dividing the sum by industry revenue. 

This increase may be thought of as an average price increase 

required to recover control costs within the industry. After 

estimating the market price increase, the expected reduction in 

industry output was then calculated, using additional information 

regarding price elasticity estimates. The impact on industrywide employment was also calculated, assuming that employment is 

proportional to output. 

 The market price increase calculation indicated that 

implementation of the controls will result in a primary aluminum 

market price increase of less than one percent. As a result of 

the low market price increase and relatively inelastic demand, 

the corresponding changes in output, employment, and total 

revenue were also low (all less than one percent). Therefore, 

the economic impact analysis estimates that the proposed rule 

will not result in significant economic impacts for the primary 

aluminum industry. 
55 

 4.5 Non-air Quality Health and Environmental Impacts

 4.5.1 Deposition. Fluoride and POM deposition on waters, 

such as the Great Lakes, is of mounting concern. Several 

references to this problem are included in the Report to Congress 

on the Great Waters Program. Implementation of the program 

recommendations would reduce emissions at many of the plants by 

50 percent, including plants near the Great Lakes and those in 

the Midwest, which also are contributors due to the long-distance 

air transport of pollutants. 

 4.5.2 Water. A wet primary control system generates about 

0.1 pound of fluorides per ton of aluminum and 0.2 pounds of 

total suspended solids per ton of aluminum. Four plants use 

scrubbers in their primary control system, and one plant plans to 

replace the existing wet systems with dry alumina scrubbers. As 

discussed above, the dry scrubbers do not control SO2. Assuming 

that SO2 requirements are not changed and these plants continue 

to use wet SO2 scrubbers following the dry alumina scrubber, no 

significant decrease is expected in the quantity of wastewater 

generated by implementation of the proposed standard. Wastewater 

quality may be improved because most of the fluorides and 

particulates will be recovered by the dry scrubber and returned 

to the process. 

 4.5.3 Solid Waste. Solid waste generated from air 

emissions control in this industry is a direct result of wet air 

emission control devices and the accompanying wastewater 

treatment. Wet scrubbers and wet ESPs generate 120 to 154 pounds 

of solid waste per ton of aluminum, which results in 6,000 to 

15,000 tpy for model plants ranging in size from 100,000 to 

200,000 tpy. Because all the captured solids are returned to the 

process with dry scrubbers, the MACT standard has the potential 

to reduce solid waste generation by the same amount. 

 4.6 Energy Impacts 

 The electrical consumption to produce aluminum is estimated 

at 6 to 7 kwh per ton of aluminum (12,000 to 14,000 kwh/ton). 

The increase in energy consumption is estimated as an average of 

145 kwh/ton for four plants. No significant effect on energy 

consumption for anode baking and paste production is expected to 

occur when control devices are replaced, although consumption 

will increase for those plants that have no controls. 
 APPENDIX A 
TECHNICAL NOTE: RATIONALE FOR SUBCATEGORIES OF SOURCES 

FOR THE PRIMARY ALUMINUM INDUSTRY 

1.0Purpose

 The purpose of this note is to identify the subcategories of 

sources to be used in determinations of maximum achievable 

control technology (MACT) for the primary aluminum industry and 

to provide the rationale for subcategorization. 

2.0 Summary

 The analysis of aluminum production processes and their 

operation resulted in the seven subcategories for the aluminum 

smelting operation given in Table 1. 

TABLE 1. ALUMINUM SMELTING SUBCATEGORIES

Number of 

Subcategory Potlines Plants

Large center-worked prebake - CWPB1 24 8 

Small center-worked prebake - CWPB2 36 6 

Center-worked prebake (producing high 

purity aluminum) - CWPB3 

4 1 

Side-worked prebake- SWPB 5 2 

Vertical stud Soderberg (in moderate 

climates)- VSS1 

5 2 

Vertical stud Soderberg (in cold climates)- 

VSS2 

5 1 

Horizontal stud Soderberg- HSS 12 3 

 Totals 91 23 

 The criteria used in developing these subcategories are 

based on air pollution control engineering differences and 

include consideration of the variations in process operation, 

emission characteristics, and control device applicability. 

Details are provided in the following sections. 

3.0 Approach

 Section 112(d) of the Clean Air Act (as amended on 

November 15, 1990) requires the Administrator to establish 

emission standards for each category or subcategory of major 
2 

sources and area sources of hazardous air pollutants listed for 

regulation. The criteria used to develop subcategories are based 

on air pollution control engineering differences. The criteria 

include consideration of process operations (including 

differences between batch and continuous operations), emission 

characteristics, control device applicability and costs, safety, 

and opportunities for pollution prevention. 

 The approach used in this analysis is based on 

characterizing differences among aluminum smelting processes and 

control device applicability and evaluating these differences 

with respect to the criteria given above for developing 

subcategories. 

4.0 Details

 There are significant differences among several aluminum 

smelting processes that affect control device applicability, 

especially the hooding for the primary collection system and its 

capture efficiency, and emission characteristics. The rationale 

for the specific subcategories is provided step by step in the 

following sections, and the approach is illustrated schematically 

in Figure 1. The criteria and applicability are summarized in 

Table 2. 

4.1 Prebake and Soderberg Processes

 Prebake and Soderberg are two distinctly different processes 

for smelting that present different challenges for capturing 

emissions from the aluminum reduction cells. These two processes 

also have different emission characteristics, especially with 

respect to polycyclic organic matter (POM). A major difference 

between the two processes is that the anodes used in the prebake 

process have been formed and baked in a separate process 

operation (i.e., the anode bake furnace), whereas the Soderberg 

process bakes the anode in the reduction cell as part of the 

smelting operation.i This process difference directly affects 

emissions and results in larger quantities of organic compounds 

such as POM being emitted from the Soderberg process during 

smelting. In the prebake process, significant quantities of 

these organics are removed during the separate anode baking step, 

which results in lower POM emissions from the reduction cell. 

 Other differences between these two processes also affect 

emissions and their control. In the prebake process, spent 

anodes are periodically removed and replaced, and this operation 

directly affects secondary (fugitive) emissions. Conversely, 

"green" paste (a mixture of unbaked coke and pitch) is added in a 

semi-continuous manner to the Soderberg reduction cell to allow 
3 

it to be baked in place and to replace the anode as it is 

consumed. In addition, there are differences in the type and 

efficiency of hooding used for the two processes. In general, 
4 

TABLE 2. SUMMARY OF CRITERIA USED TO DEVELOP SUBCATEGORI

Types of processes compared

Criteria-differences in the fo

Process 

operationb

Emissions 

quantity

Capt

Prebake vs. Soderberg yes yes CWPB vs. SWPB yes yes CWPB1 vs. CWPB2 yes yes CWPB1 vs. CWPB3 no yes VSS vs. HSS yes yes VSS1 vs. VSS2 no yes 

aThese columns indicate if there are differences between the processes 

to the given criterion. Other criteria (cost, safety, pollution opportunities) were not judged to be significant for the subcateg

bDifferences in process operation that affect emissions or their contro

cThe differences are primarily in the type of capture system that can b

used and its resulting capture efficiency. CWPB = center-worked prebake HSS = horizontal stud Soderberg SWPB = side-worked prebake VSS = vertical stud Soderberg 
5 
6 
7 

the hoods used for the Soderberg process have lower capture 

efficiencies because the gases evolving from the Soderberg 

cell are more difficult to capture.ii

4.2 Center-Worked and Side-Worked Prebake

 Within the prebake process, center-worked (CWPB) and 

side-worked (SWPB) units have significant differences in 

design of the equipment, its operation, and applicable 

emission controls, especially in the capture of primary 

emissions. The process and operational differences include 

the placement of the anodes, the type of side shields used, 

the method of alumina addition, and how the reduction cells 

are worked.iii

 In the SWPB process, alumina is added along the sides 

of the reduction cell and the anodes are set close together 

near the center line. In the CWPB process, alumina is added 

down the center of the pot and the anodes are closer to the 

side. Consequently, the covers and hoods for the primary 

collection system are different for these two types of units 

because of the design, placement of anodes, and working the 

bath from the center versus from the side. In addition, the 

newer CWPB units can be equipped with computer-controlled 

crust breakers and point feeders, which often allow them to 

be worked without removing the side shields. 

 The design and operational differences between SWPB and 

CWPB result in different design considerations for the 

primary collection system. In general, emissions from the 

CWPB reduction cells can be captured with a higher 

efficiency than those from SWPB cells.iv

4.3 Subcategories for Center-Worked Prebake

 The investigation of the CWPB process indicates that 

there are two different designs that directly affect the 

ability of the operator to control emissions. One group is 

composed of CWPB reduction cells that are larger, generally 

newer, and operate at higher amperages than the older and 

smaller CWPB units. The major factor affecting the

difference in emissions and controls for the two types of 

units is the number of anode changes required. More 

frequent anode changes result in greater quantities of 

secondary (fugitive) emissions that are difficult to capture 

and control. 

 There are other differences between the large and small 

CWPB units that affect emissions and their capture. Access 
8 

is required more often to the smaller units because they are 

generally more unstable and are less likely to have computer 

controls. More frequent access means the shields of the 

primary collection system are opened more frequently and 

perhaps for longer periods, which results in poorer emission 

capture and higher emissions. Another factor is the smaller 

units generally have more anodes per reduction cell, which 

affects the design and capture efficiency of the hooding.v

 

These combinations of factors indicate that the larger CWPB 

units have lower emissions per ton of aluminum produced and 

that less emissions escape capture by the primary collection 

system. 

 A separate subcategory was developed for four centerworked prebake potlines with wet primary control systems 

(CWPB3). These potlines produce a high purity aluminum for 

a specialized market, and they can do so only because metal 

impurities are removed with the sludge from the wet

scrubbers. If these potlines were required to install dry 

alumina scrubbers, the contaminants would be returned to the 

reduction cell and contaminate the aluminum. The company 

claims that if they must meet MACT for the prebake 

subcategory of modern potlines with dry alumina scrubbers, 

they could lose their market for high purity aluminum. The 

EPA is requesting comments on the issue of a separate 

subcategory for plants that produce high purity aluminum. 

4.4 Horizontal and Vertical Stud Soderberg

 There are two distinct designs used in the Soderberg 

process: horizontal stud (HSS) and vertical stud (VSS). As 

the names imply, in one case the steel studs that carry 

current project vertically through the unbaked paste and 

into the baked portion of the anode, and in the other case 

the studs project horizontally. The differences in design 

and operation result in different types of hooding and 

evacuation rates, both of which affect emissions and 

controls. In the VSS cell, the stationary anode casing and 

vertical projection of the studs through the anode allow the 

installation of a gas collection skirt between the anode 

casing and bath. The collected gases are ducted to 

burners where carbon monoxide, tars, and other hydrocarbons 

are burned prior to the primary control device.vi

 The design of the HSS cell prevents the installation of 

integral gas collection because the anode casing is formed 

by removable channels that support the studs, and these 

channels must be periodically changed as the anode moves 

downward. Consequently, the hooding for the HSS cell is 
9 

restricted to a design that results in air infiltration and 

dilution. The gases from the HSS cell are too dilute to 

support combustion in burners.vii A typical VSS cell has an 

evacuation rate on the order of 500 ft3

/min compared to a 

range of 3,500 to 5,000 ft3/min for an HSS cell.viii

4.5Vertical Stud Soderberg with and without wet roof 

scrubbers

 Two VSS plants with five potlines use wet roof 

scrubbers to control secondary emissions, and the third 

plant also with five potlines uses work practices for 

secondary emission control. Consequently, the EPA 

investigated the use of wet roof scrubbers as the MACT floor 

technology for all VSS plants. However, data obtained from 

Intalco Aluminum (in Ferndale, WA) on their wet roof 

scrubber operation indicated that their scrubbers were shut 

down in periods of cold weather to avoid damage to the 

scrubbers and water treatment plant. 

 The data from Intalco indicated that their scrubbers 

were shut down due to cold weather an average of 36 days per 

year (a range of 19 to 48 days/year from 1986 to 1993). 

This represents a down time of 10 percent, i.e., they 

operate about 90 percent of the year. The procedure used at 

Intalco is to shut the scrubbers down when the temperature 

reaches 27°F and the temperature is predicted to drop 

further. 

 The VSS plant without roof scrubbers in located in

northern Montana where the weather is much colder than that 

in Ferndale. Data obtained from the National Weather 

Service for Kalispell, MT, which is near the location of 

Columbia Falls' VSS plant, indicated that the normal daily 

average temperature was below 27°F about 21 percent of the 

time and the normal daily low temperature was below 27°F 

about 40 percent of the year. Consequently, the use of wet 

roof scrubbers based on Intalco's experience suggests that 

scrubbers installed in northern Montana could be shut down 

on the order of 20 to 40 percent of the time. 

 In assessing the achievability of a technology-based 

standard, EPA must show that a standard is capable of being 

met under most adverse conditions that can reasonably be 

expected to occur. The EPA determined that wet roof 

scrubber technology has not been adequately demonstrated for 

very cold climates and is not applicable as the MACT floor 

technology for the VSS plant in Montana. Consequently, a 

separate subcategory (VSS2) was created for the five VSS 
10 

potlines in Montana, and the MACT floor for this subcategory 

would be determined by the average emission limitation 

achieved by these five potlines. 

12 

5.0 References

i.Primary Aluminum: Guidelines for Control of Fluoride 

Emissions from Existing Primary Aluminum Plants. EPA450/2-78-049b. December 1979. 

ii.Reference 1. 

iii.Reference 1. 

iv.Reference 1. 

v.Memorandum from Ours, K. D., Research Triangle Institute, to W. 

S. Fruh, EPA/ISB. June 10, 1994. Summary of Meeting with 

Aluminum Industry Representatives. 10 pp. 

vi.Reference 1. 

vii.Reference 1. 

viii.Compiled from responses by each plant in the industry to 

Information Collection Requests issued under Section 114 of 

the Clean Air Act Amendments. 
 APPENDIX B: MACT FLOOR DETERMINATIONS

I. Purpose:

 The purpose of this technical note is to explain how 

emission limits for the MACT floor sources were developed. 

II. Approach:

 The averages of the top five potlines were used as the basis 

for determining the MACT floor because there were fewer than 30 

sources in each category or subcategory. For potlines, the 

median potline (i.e., the third best performing among the five 

best performing) was chosen to represent the average emission 

limitation achieved by the top five. Historical data for total 

fluoride for the MACT floor potlines were used and were 

supplemented by additional data collected during the MACT test 

program, especially for polycyclic organic matter (POM). The 

data are given in EPA's rulemaking docket for primary aluminum 

and are also listed in Appendix D of this document.

 The overall approach included evaluating historical data 

when available, identifying any values not representative of 

normal operation, and determining the level of control that had 

been achieved by the MACT floor potline. When historical data 

were not available (e.g., for POM), a statistical approach based 

on estimation of upper confidence levels was used to determine 

the level of control that had been achieved. 

III. Results:

 A. Total Fluoride from Potlines

 The historical data for total fluoride (TF) were reviewed 

and discussed with the various companies to identify and delete 

"outliers", which are values that are not representative of 

normal operation. The historical data were then analyzed in the 

way the rule will be implemented -- as monthly averages. The 

emission limits for the MACT floor for TF were chosen from the 

review of the data from the highest monthly averages in the data 

set. This approach ensures that the limits for TF associated 

with the MACT floor have been achieved by the MACT floor potlines 

on which they are based. [See Appendix D for the listing of 

monthly averages for the MACT floor potlines.] 

 Adequate historical data for TF were available to 

characterize the MACT floor for the following subcategories of 

potlines as identified in Appendix A: CWPB1, CWPB2, SWPB, HSS, 

VSS1, and VSS2. The results (MACT floor limits) are summarized 

in Table 1. 
2 

 There were very few historical data available for the CWPB3 

subcategory, and the plant that comprises the subcategory 

indicated that major improvements had been made or were underway 
3 

 TABLE 1. SUMMARY OF MACT FLOOR DATA FOR POTLINES TABLE 1. SUMMARY OF MACT FLOOR DATA FOR POTLINES (lb TF/ton) lb TF/ton) lb TF/ton)

Plant N Meana Standard 

deviation 

MACT floor 

limit 

Comment

Noranda Line 3 (CWPB1) 

46 1.13 0.32 1.9 45 monthly averages, 1/89-12/92

results 

Kaiser-Mead Line 1 (CWPB2) 

13 2.18 0.49 3.0 12 monthly averages (generally 

8/93-7/94, plus MACT program 

Intalco Line C (SWPB) 45 0.97 0.26 1.6 45 monthly averages, 1/90-12/93

Monthly roof and 12-mo averag

Kaiser-Tacoma Line 2 (HSS) 

23 2.07 0.36 2.7 22 monthly averages, 3/93-12/94

results 

Columbia-Goldendale Line 1 (VSS1) 

31 1.31 0.42 2.2 30 monthly averages, 1/92-6/94, 

results 

Columbia Falls (VSS2) 7 2.22 0.31b 2.7 7 averages of 3 runs, 10/94-12/9Mt. Holly A & B 26 0.81 0.14 1.2 26 monthly averages 1/89-12/92 

a These mean values also include emissions from the primary control system. b The standard deviation was obtained from historical data submitted by the company.
4 

to reduce both secondary emissions and emissions from the wet 

scrubbers used for the primary control system. The available 

data and information from the plant indicated that a study of 

their system showed they had achieved a level of performance that 

would ensure that they are meeting a monthly limit of 

2.5 lb/ton.20 Consequently, the EPA determined that a TF limit of 

2.5 lb/ton represented the MACT floor for CWPB3. 

B. POM from Soderberg Potlines

 The results of the analysis of POM emissions from HSS 

potlines are summarized in Table 2. For the HSS subcategory, the 

MACT floor was determined from the 95th percentiles for the 

averages of 3 runs for both primary and secondary POM emissions. 

 The result was a MACT floor level of 4.7 lb POM/ton from the sum 

of 2.7 (secondary emissions) and 2.0 lb/ton (primary system 

emissions). 

 The POM limits for VSS1 are based on the limited test data 

available from one potline at Columbia-Goldendale and one potline 

at Northwest Aluminum. The results from these two potlines were 

combined to provide enough data to assess performance and to 

represent the MACT floor. These two potlines achieved a level of 

2.4 lb/ton. There were no validated POM data available for the 

VSS2 subcategory; however, POM data for the VSS1 subcategory 

before the wet roof scrubbers represent the same process 

configuration as that for VSS2. Consequently, the VSS1 POM data 

were used to derive limits for VSS2. The POM emissions at the 

inlet to the wet roof scrubbers did not exceed 3.7 lb/ton. 

C. POM Limit for New Potlines 

 A POM limit was derived for new potlines based on the data 

from sampling at Noranda's Line 3. The average POM from roof 

sampling was 0.106 lb/ton, and the values from the primary system 

were 0.426, 0.115, and 0.088. The roof emissions were added to 

the primary system results to obtain three data points with an 

average of 0.316 and a standard deviation of 0.188. The 95th 

percentile was chosen as the MACT floor for new potlines: 

95th percentile = 0.316 + 1.645 * 0.188 = 0.63 lb/ton

D. POM and TF Emissions from Anode Bake Furnaces

 

 

20 Memorandum from W. Hill, Southwire Company, to M. McKeever, 

EPA/OAQPS/ESD, dated May 23, 1995. 
5 

 Data for anode bake furnaces are given in Table 3 for both 

TF and POM. The results for anode bake furnaces were converted 

 
6 

 TABLE 2. SUMMARY OF MACT FLOOR POM DATA FOR HSS P TABLE 2. SUMMARY OF MACT FLOOR POM DATA FOR HSS POTLINES (lb/ton) TLINES (lb/ton) TLINES (lb/ton) 

Plant N Mean Standard 

deviation 

MACT floora Comments 

Kaiser-Tacoma Line 2 (HSS): secondary (roof) emissions 

5 1.82 0.52 2.7 Based on averages of 3 runs from 

program results 

Kaiser-Tacoma Line 2 (HSS): primary system emissions 

3 0.781 0.756 2.0 Based on averages of 3 runs from 

program results 

a Based on the 95th percentile from (mean + 1.645 * standard deviation). 
7 

TABLE 3. SUMMARY OF M TABLE 3. SUMMARY OF M TABLE 3. SUMMARY OF MACT FLOOR DATA FOR BAKE FURNA ACT FLOOR DATA FOR BAKE FURNACES (lb/ton of anode) ACT FLOOR DATA FOR BAKE FURNACES (lb/ton of anode) CES (lb/ton of anode) 

Plant N Mean Standard 

deviation 

Comments 

Noranda -- TF 33 0.070 0.118 Averages of 3 runs (96 individual runs 

9/83-7/93 plus 4 runs from MACT test 

program) 

Alumax- Mt. Holly 

-- TF 

9 0.0071 0.0065 9 individual runs 1992-1994 

 3 0.0071 0.0056 Averages of 3 runs 

Kaiser-Mead -- TF 3 0.013 0.007 3 individual runs, MACT test program 

Noranda -- POM 3 0.025 0.012 3 individual runs, MACT test program 

Kaiser-Mead -- 

POM 

3 0.16 0.011 3 individual runs, MACT test program 
8 

from lb/ton of aluminum to lb/ton of anode by multiplying by 2. 

 There are eight bake furnaces currently subject to the NSPS 

level of 0.20 lb/ton anode, and these bake furnaces include the 

top 5 best performing in the industry. A review of the available 

data indicated that the NSPS level represented the average limit 

achieved by the top five, and it also represented a level of 

control demonstrated by the data as achievable. Consequently, 

the EPA determined that 0.20 lb/ton anode represented the MACT 

floor for TF emissions from bake furnaces. 

 The MACT floor for POM from bake furnaces was based on data 

collected at Kaiser-Mead during the MACT floor test program, 

which indicated a level of 0.18 lb POM/ton had been achieved. 

The TF limit for new bake furnaces was based on data from Alumax 

that showed a level of 0.02 lb TF/ton had been achieved (at the 

99th percentile). The best-performing bake furnace for which POM 

data were available was Noranda's furnace that showed a level of 

0.05 lb POM/ton had been achieved (at the 99th percentile). 

IV. Emissions Averaging

A. Total fluoride from potlines

 An approach is presented here to develop a mechanism to 

allow emissions averaging across multiple potlines. The approach 

attempts to provide a rough estimate of the standard deviation 

when averaging across multiple potlines for comparison to a 

monthly average limit. When averaging is used, the variability 

(standard deviation) decreases. Consequently, the approach 

attempts to derive limits that will ensure that emissions do not 

increase above the levels expected if each potline had to comply 

with the monthly limit for an individual line. 

 The approach is based on reducing the standard deviation for 

the MACT floor potlines by the square root of "N" (i.e., dividing 

by the square root of N), where N is the number of potlines that 

will be used for emission averaging at a specific plant. The 

mean and standard deviation used for each subcategory are given 

in Table 4. These values were used in the equation given below 

to calculate limits for emission averaging for each subcategory 

for different numbers of potlines that might be used in the 

averaging approach. The results are summarized in Table 5. 

 Averaging limit = mean + z*(sd/N0.5) 

where: 
9 

"z" is the constant representing the 95th (1.645) or 99th (2.326) 

percentile, 

"sd" is the standard deviation from Table 4, and 

"N" is the number of potlines used in averaging. 

For example, the average for CWPB2 (Kaiser-Mead) was 2.18 lb/ton 

and the standard deviation was 0.49. For the case of averaging 

across 3 potlines, the limit is calculated as: 

 Limit (3 lines) = 2.18 + 2.326*(0.49)/30.5 = 2.8 lb/ton. 

 For the CWPB3 category for which there were no useful 

historical data, the single potline limit of 2.5 lb/ton was 

assumed to represent the 99th percentile and the standard 

deviation was assumed to be similar to that for CWPB1. The mean 

that would be needed to achieve a limit of 2.5 lb/ton was then 

calculated from: 

 Mean = 2.5 - 2.326*0.32 = 1.8 lb/ton. 
10 

TABLE 4. SUMMARY OF VALUES USED FOR CALCULATING E TABLE 4. SUMMARY OF VALUES USED FOR CALCULATING EMISSION 

 AVERAGING LIMITS FOR TF AVERAGING LIMITS FOR TF 

Subcategory Total fluoride (lb/ton) z 

 Mean Standard deviation 

CWPB1 1.13 0.32 2.326 

CWPB2 2.18 0.49 2.326 

CWPB3 1.80 0.32 2.326 

SWPB 0.97 0.26 2.326 

HSS 2.07 0.36 1.645* 

VSS1 1.31 0.42 2.326 

VSS2 2.22 0.31 1.645* 

* The constant for the 95th percentile is used for these subcategories to be consistent with the derivation of 

the single line limit and to ensure that emissions do not increase from averaging emissions. 

TABLE 5. POTLINE TF AND POM LIMITS FOR EMISSIONS TABLE 5. POTLINE TF AND POM LIMITS FOR EMISSIONS AVERAGING VERAGING

Type Monthly TF limit (lb/ton) for given number of potlines 

 2 lines 3 lines 4 lines 5 lines 6 lines 7 lines 8 lines 

CWPB1 1.7 1.6 1.5 1.5 1.4 1.4 1.4 

CWPB2 2.9 2.8 2.7 2.7 2.6 2.6 2.6 

CWPB3 2.3 2.2 2.2 2.1 2.1 2.1 2.1 

VSS1 2.0 1.9 1.8 1.7 1.7 1.7 1.7 

VSS2 2.6 2.5 2.5 2.4 2.4 2.4 2.4 

HSS 2.5 2.4 2.4 2.3 2.3 2.3 2.3 

SWPB 1.4 1.3 1.3 1.2 1.2 1.2 1.2 

 Monthly POM limit (lb/ton) for number of potlines

HSS 4.1 3.8 3.7 3.5 3.5 3.4 3.3 

VSS1 2.1 2.0 1.9 1.9 1.8 1.8 1.8 

VSS2 3.4 3.2 3.2 3.1 3.1 3.0 3.0 
11 
12 

B. POM from potlines

 Emission averaging limits for POM are derived for KaiserTacoma and the HSS subcategory in the same manner described 

earlier. The mean and standard deviations from Table 2 are used 

in the example calculations given below: 

 Monthly limit when averaging across 3 potlines: 

 Primary control system 

 Limit = 0.781 + 1.645 (0.756)/(3)0.5 = 1.5 lb/t 

 Secondary emissions 

 Limit = 1.82 + 1.645 (0.52)/(3)0.5 = 2.3 lb/t

 For the VSS1 subcategory, the approach is based on the test 

results for POM from the wet roof scrubbers with an average of 

1.42 lb/ton and a standard deviation of 0.92. The value of "z" 

was calculated from the mean, standard devation, and the single 

line limit of 2.4 lb/ton: 

 z = (2.4 - 1.42)/0.92 = 1.065. 

This value of z was then used to calculate emission averaging 

limits as in the example when averaging across 3 potlines: 

 Limit = 1.42 + 1.065 (0.92)/(3)0.5

 = 2.0 lb/t

 For the VSS2 subcategory, the approach is based on the test 

results for POM at the inlet to the wet roof scrubbers with an 

average of 2.63 lb/ton and a standard deviation of 1.04. The 

value of "z" was calculated from the mean, standard devation, and 

the single line limit of 3.7 lb/ton: 

 z = (3.7 - 2.63)/1.04 = 1.029. 

This value of z was then used to calculate emission averaging 

limits as in the example when averaging across 3 potlines: 

 Limit = 2.63 + 1.029 (1.04)/(3)0.5

 = 3.2 lb/t

C. Total fluoride from bake furnaces

 Emissions averaging limits for fluoride from bake furnaces 

were derived from the data for Noranda's bake furnace and are 

based on a log normal distribution. The log average was -3.467 

and the standard deviation (log form) was 1.154. An example 

calculation is given below for averaging across 3 bake furnaces: 
13 

Limit = exp [-3.467 + 1.645 (1.154)/(3)0.5]=exp[-2.37] = 0.09 lb/t 

Repeating this process for different numbers of bake furnaces 

gives the limits listed in Table 6. 

D. POM from bake furnaces 

 POM limits for bake furnaces were derived from the data from 

the tests at Kaiser-Mead. The very small standard deviation 

resulted in emissions averaging limits with the same value as 

that for a single bake furnace (0.17 lb/ton). These results are 

also summarized in Table 6. 

 TABLE 6. EMISSIONS AVERAGING LIMITS FOR BAKE FURNACES 

Number of furnaces Averaging limits (lb/t of anode)

 TF POM 

2 0.12 0.17 

3 0.09 0.17 

4 0.08 0.17 

5 0.07 0.17 
 APPENDIX C: EVALUATION OF WET ROOF SCRUBBERS AS A CONTROL 

 OPTION FOR SECONDARY EMISSIONS--BEYOND THE FLOOR

I. Purpose:

 The purpose of this note is to estimate the impacts of 

installing wet roof scrubbers for the control of secondary 

emissions from aluminum smelting. Wet roof scrubbers are being 

considered as an option for a level of control that is more 

stringent than the MACT floor (i.e., "beyond the MACT floor"). 

II. Approach:

 Estimates are provided for three cases: 1) a plant that 

already has wet roof scrubbers installed, 2) retrofitting the 

scrubbers at a vertical stud Soderberg (VSS) plant that has good 

control of secondary emissions through improved operation and 

maintenance, and 3) installing the scrubbers on a new centerworked prebake (CWPB) plant that has good control of secondary 

emissions through improved operation and maintenance, new 

hooding, and automated controls. Estimates of impacts are 

presented for emission reductions and costs, and the effects on 

solid waste generation and wastewater are discussed. 

III. Estimates of Emission Reduction

 Northwest Aluminum currently has wet roof scrubbers on their 

VSS potrooms and was chosen to represent the first case 

(evaluation of a plant that already has wet roof scrubbers). 

Emission testing was conducted at this plant for EPA in 

August 1993.1

 Table 1 is a summary of the test results for 

controlled and uncontrolled emission rates and control efficiency 

for the wet roof scrubbers. 

 The control efficiencies for the different pollutants from 

the tests at Northwest Aluminum are used in this analysis to 

estimate the potential for emission reduction if wet roof 

scrubbers were retrofitted at an existing facility or included in 

the construction of a new facility. For these two cases, the 

actual percent emission reduction may be less than that from 

Northwest Aluminum because these other plants would have lower 

concentrations of pollutants entering the scrubbers. 

 Columbia Falls Aluminum Company (CFAC) is a VSS plant that 

controls secondary emissions using improved operation and 

maintenance without wet roof scrubbers. This plant will be used 

to represent the second case of retrofitting wet roof scrubbers 

at an existing plant. CFAC reported TF emission rates of 

2.1 lb/ton and gaseous fluoride rates of 1.0 lb/ton from testing 

the potrooms using Methods 13 and 14.2

 

TABLE 1. TEST RESULTS FOR THE WET ROOF SCRUBBERS AT 

NORTHWEST ALUMINUM 
2 

Pollutant Inlet 

(lb/ton) 

Outlet 

(lb/ton) 

Percent 

control 

Reduction 

(lb/ton) 

Particulate matter 38.7 17.5 55 21.2 

Polycyclic organic 

matter 

3.7 1.8 51 1.9 

Gaseous fluoride 3.0 0.39 87 2.6 

Total fluoride 10.4 2.0 80 8.4 

 POM emissions from CFAC are estimated from the ratio of 

POM:GF entering the scrubbers from the Northwest Aluminum test 

(1.2). Particulate matter emissions for CFAC are based on the 

ratio of PM:TF measured at Northwest Aluminum (3.7). 

 Table 2 presents the TF and GF emission rates reported by 

CFAC and the PM and POM emission rates estimated from the ratios. 

The reduction in emissions that would be achieved by retrofitting 

wet roof scrubbers is estimated from the control efficiencies 

measured at Northwest Aluminum. [Note: For this analysis, 

estimates of gaseous fluoride are based on the back-half analysis 

of fluoride that passes through the front-half filter.] 

TABLE 2. ESTIMATED EMISSION REDUCTIONS FROM RETROFIT OF WET ROOF 

SCRUBBERS AT COLUMBIA FALLS ALUMINUM 

Pollutant Inlet 

(lb/ton) 

Outlet 

(lb/ton) 

Percent 

control 

Reduction 

(lb/ton) 

PM 7.8 3.5 55 4.3 

POM 1.2 0.6 51 0.6 

GF 1.0 0.13 87 0.87 

TF 2.1 0.4 80 1.7 

 Alumax of South Carolina is a relatively new and well 

controlled CWPB plant without wet roof scrubbers. This plant was 

chosen for the evaluation of wet roof scrubbers on new plants. 

Alumax reported TF and GF data from their potrooms as shown in 

Table 3.3 The POM emissions were estimated as less than 0.3

lb/ton from the test results at Noranda4

, which is also an NSPS 

CWPB plant. PM emissions were estimated from the ratio of PM:TF 

(3.3) measured at another CWPB plant (Kaiser, Mead).

5

 
3 

 Table 3 presents the reported TF and GF emission rates for 

Alumax and the estimated PM and POM emission rates from the 

ratios from other tests. The table also gives the estimated the 

reduction in emissions that might be achieved from wet roof 

scrubbers (assuming the same control efficiencies as those 

reported in the Northwest Aluminum test). 

TABLE 3. ESTIMATED EMISSION REDUCTIONS FROM RETROFIT OF WET ROOF 

SCRUBBERS AT ALUMAX

Pollutant Inlet 

(lb/ton) 

Outlet 

(lb/ton) 

Percent 

control 

Reduction 

(lb/ton) 

PM 2.4 1.1 55 1.3 

POM <0.3 <0.15 51 <0.15 

GF 0.37 0.05 87 0.32 

TF 0.73 0.15 80 0.58 

IV. Cost Estimate:

 In 1975, Columbia Falls Aluminum Company estimated the cost 

of installing SF-type multiventuri wet roof scrubbers and a 

wastewater treatment system to be $20,540,000. The Marshall & 

Swift Equipment Cost Index published in Chemical Engineering 

Magazine was used to convert the 1975 cost estimate into 1994 

dollars, which is $45,319,000 or $245 per ton of annual capacity. 

 In 1970 Northwest Aluminum installed wet roof scrubbers at a 

total cost of $5,255,000. In 1990, the same plant installed a 

water treatment pond at a cost of $2,400,000. The total cost in 

1994 dollars is approximately $19,556,000 or about $223 per ton 

of annual capacity. 

 The average of the two capital costs is $234 per ton of 

annual capacity. For an estimated life of 30 years, the capital 

recovery factor is 0.081, which yields an annual cost of capital 

of $19/ton. 

 Operating costs provided from responses to information 

collection requests averaged about $8.57/ton aluminum for those 

plants that currently have wet roof scrubbers. Adding the 

operating cost to the annual cost of capital gives a total 

annualized cost of about $27.60/ton. 

V. Estimate of Cost Effectiveness:
4 

 The estimate of total annualized cost is used in Table 4 

along with the annual emission reduction developed earlier to 

estimate the cost effectiveness for the three cases. Cases 2 and 

3 are of primary interest because they represent the cost 

effectiveness of retrofitting wet roof scrubbers at an existing 

plant (Case 2) and incorporating wet roof scrubbers into the 

construction of a new plant (Case 3). The cost effectiveness for 

HAPs ranges from about $38,000 to over $120,000/ton for these two 

cases. 

TABLE 4. ESTIMATES OF COST EFFECTIVENESS OF WET ROOF SCRUBBERS

 

 Case 1 

(existing 

VSS) 

Case 2 

(retrofit 

to VSS) 

Case 3 

(new CWPB)

Capacity (t/yr) 88,000 185,000 200,000 

Capital cost ($) 20,600,000 43,000,000 47,000,000

Total annualized cost ($/yr) 2,400,000 5,100,000 5,500,000 

PM reduction (t/yr) 930 400 130 

POM* reduction (t/yr) 84 56 <15 

GF* reduction (t/yr) 114 80 32 

TF reduction (t/yr) 370 157 58 

HAP* reduction (t/yr) 198 136 47 

Cost effectiveness for PM 

($/ton PM) 

2,600 13,000 42,000 

Cost effectiveness for POM 

($/ton POM) 

29,000 91,000 >370,000 

Cost effectiveness for GF 

($/ton GF) 

21,000 64,000 170,000 

Cost effectiveness for TF 

($/ton TF) 

6,500 32,000 95,000 

Cost effectiveness for HAPs 

($/ton GF + POM) 

12,000 38,000 120,000 

*GF is assumed to be primarily hydrogen fluoride for the purpose 

of estimating emissions of HAPs. POM are represented by using 

methylene chloride extractables as a surrogate. 
5 

VI. Other Impacts:

 The use of wet roof scrubbers increases the use of

electricity and water, and the scrubbers generate a sludge and 

wastewater stream. Data from two plants with wet roof scrubbers 

indicated that sludge is generated at a rate of 9 to 26 lb/t 

aluminum and wastewater is generated at a rate of 100 to 600 

gal/min.6

 Using a midrange value of 18 lb/t for solid waste

generation, the quantity of sludge produced for the three example 

plants ranges from about 800 to 1,800 t/yr (for capacities of 

88,000 to 200,000 t/yr). Increased electrical usage is estimated 

as 300 kwh/t aluminum for the operation of wet roof scrubbers and 

lime treatment of the water.7

VII. References:

1.Emissions Measurement Test Report - Northwest Aluminum Company. 

 Prepared by Entropy, Inc. June 1994. 77 p. 

2.Data provided by Don Ryan, Columbia Falls Aluminum, Montana, to 

Steve Fruh, EPA. January 1995. 

3.Data submitted by the Aluminum Association: "Total Fluoride 

Emission Assessment." Covers the period from January 1989 

through December 1992. 

4.Noranda Aluminum, Inc. Method 5/POM and 13B Testing - New 

Madrid, Missouri - September 14-20, 1994. Prepared by 

AmTest Air Quality, Inc. January 10, 1994. pp. 1 through 

62. 

5.Kaiser Aluminum and Chemical Corporation Method 5/POM and 13B 

Testing - Mead, Washington - March 15-24, 1994. Prepared by 

AmTest Air Quality, Inc. November 9, 1994. pp. 1 through 

99. 

6.Compiled from responses by each plant in the industry to 

information collection requests. 

7.Primary Aluminum: Guidelines for Control of Fluoride Emissions 

from Existing Primary Aluminum Plants. U.S. Environmental 

Protection Agency. Report No. EPA-450/2-78-049b. December 

1979. p. 9-33. 
 APPENDIX D. COMPLETE LISTING OF MACT FLOOR DATA 
1 

 MACT FLOOR DATA

 A brief description of the tables is given below. In 

general, the analysis focused on the monthly averages (generally 

3 to 4 runs per month) for secondary (roof) emissions except for 

plants with wet roof scrubbers. The monthly averages for wet 

roof scrubbers were composed of tests of 3 to 6 fans per month. 

Table 1: The data for Mt. Holly Lines A and B were provided by 

the Aluminum Association in a submittal commonly referred to as 

the "blue book" data.1

 Alumax provided corrections for several 

data points for Line B.2 Results are for both primary and 

secondary emissions. 

Table 2: The data for Columbia-Goldendale were submitted by the 

company

3

 and are the monthly averages from sampling four fans 

each month. 

Table 3: The data for Noranda were submitted by the company and 

represent individual runs for secondary emissions.4

 The results 

of a test conducted for the MACT test program (labeled "Amtest") 

were also added to the data set.5

Table 4: The Columbia Falls data (secondary emissions only) were 

collected by EPA Methods 13/14 and submitted by the company.

6

 

The original data submitted by the Aluminum Association were 

based on a method developed by the company (i.e., not EPA 

methods). 

Table 5: The data for Kaiser-Tacoma (secondary emissions only) 

were submitted by the company and were collected by EPA 

Methods 13/14.7 The results of a test conducted for the MACT 

test program (labeled "Amtest") were also added to the data set.8

 Data submitted prior to this were not based on EPA methods. 

Table 6: The data for Kaiser-Mead (secondary emissions only) 

were submitted by the company and were collected by EPA 

Methods 13/14.9 The results of a test conducted for the MACT 

test program (labeled "Amtest") were also added to the data set.10

Table 7: The data for Intalco were submitted by the company

11 and 

were calculated from kg/day of total fluoride and monthly 

aluminum production. The results for both primary and secondary 

emissions are given for each run. A total of six fans are 

sampled each month, along with four runs for the primary system. 

 A total of 3 scrubber tests out of 262 total were identified as 

outliers (2.7 to 3.2 lb/ton in January 1991). 
2 

Table 8: This analysis uses monthly averages for the wet roof 

scrubbers and adds a 12-month rolling average for the primary 

system to the monthly average of the scrubbers. (This is the way 

the rule is expected to be implemented.) 

Table 9: This table presents the HSS POM data for secondary and 

primary emissions for Kaiser-Tacoma.12 These data were collected 

as part of the MACT test program. Data for VSS1 are also 

included from tests conducted under the MACT program at ColumbiaGoldendale and Northwest Aluminum.13, 14, 15

Table 10: The bake furnace data for Noranda were submitted by 

the company and were analyzed as the average of three runs.

16

Table 11: Data for the bake furnace at Mt. Holly were submitted 

by the company.17 Results shown for Kaiser-Mead and Noranda were 

collected under the MACT test program.18, 19
3 

 TABLE 1. ALUMAX MT. HOLLY -- TOTAL FLUORIDE

 Line A Line B 

MONTH (lb/ton) MONTH (lb/ton) 

3/89 0.77 1/89 0.81 

7/89 0.77 5/89 0.74 

11/89 1.02 9/89 0.96 

1/90 0.67 2/90 0.68 

4/90 0.63 6/90 0.75 

8/90 1.17 10/90 0.78 

9/90 0.74 3/91 0.72 

12/90 0.84 7/91 0.89 

1/91 0.77 11/91 0.87 

5/91 0.76 4/92 0.74 

9/91 0.87 8/92 0.81 

2/92 0.56 12/92 0.63 

6/92 1.04 

10/92 0.99 

 

Avg. 0.829 0.782 

Std dev. 0.172 0.093 

N 14 12 

 

 Summary of Lines A and B 

Combined 

 

 

 Avg. 0.807 

 Std dev. 0.141 

 N 26 
4 

 TABLE 2. COLUMBIA-GOLDENDALE LINE 1 ROOF EMISSIONS 

Date lb/t TF 

1 92 2.18 

2 92 1.33 

3 92 1.55 

4 92 1.89 

5 92 0.83 

6 92 1.33 

7 92 0.69 

8 92 1.59 

9 92 0.66 

10 92 1.14 

11 92 1.32 

12 92 2.00 

1 93 0.59 

2 93 0.32 

3 93 0.90 

4 93 1.07 

5 93 1.28 

6 93 1.43 

7 93 1.51 

8 93 1.24 

9 93 1.31 

10 93 1.68 

11 93 1.46 

12 93 1.48 

1 94 1.98 

2 94 1.42 

3 94 1.43 

4 94 1.21 

5 94 1.38 
5 

6 94 1.30 

MACT test 1.05 

Avg. 1.31 

Std.dev. 0.42 

N 31 

Add 0.005 to 0.02 lb/t for primary emissions. 
6 

 TABLE 3. NORANDA LINE 3 ROOF DATA (lb TF/ton) 

Date 

TF (lb/t) 

 Single 

run 

 Monthly 

 average 

11-Jan-89 1.07 1.22 

12-Jan-89 1.40 

13-Jan-89 1.17 

14-Feb-89 0.89 0.85 

15-Feb-89 0.81 

16-Feb-89 0.84 

07-Mar-89 1.22 0.96 

08-Mar-89 0.99 

09-Mar-89 0.69 

11-Apr-89 1.02 0.80 

12-Apr-89 0.59 

13-Apr-89 0.79 

09-May-89 1.28 1.02 

10-May-89 0.79 

11-May-89 1.00 

06-Jun-89 0.92 1.01 

07-Jun-89 1.03 

08-Jun-89 1.09 

11-Jul-89 0.74 0.82 

12-Jul-89 0.70 

13-Jul-89 1.01 

08-Aug-89 0.80 1.02 

09-Aug-89 1.11 

10-Aug-89 1.16 

18-Dec-89 0.61 0.66 

19-Dec-89 0.71 

20-Dec-89 0.65 
7 

Date 

TF (lb/t) 

 Single 

run 

 Monthly 

 average 

09-Jan-90 0.59 0.92 

10-Jan-90 1.04 

11-Jan-90 1.13 

06-Feb-90 0.73 0.63 

07-Feb-90 0.65 

08-Feb-90 0.51 

06-Mar-90 1.92 1.81 

07-Mar-90 2.41 

08-Mar-90 1.09 

03-Apr-90 2.03 1.37 

04-Apr-90 0.95 

05-Apr-90 1.12 

08-May-90 0.92 0.87 

09-May-90 0.81 

10-May-90 0.87 

05-Jun-90 1.12 1.19 

06-Jun-90 1.24 

07-Jun-90 1.20 

10-Jul-90 1.37 1.59 

11-Jul-90 1.73 

12-Jul-90 1.68 

08-Aug-90 1.34 1.33 

09-Aug-90 1.13 

10-Aug-90 1.53 

11-Sep-90 1.53 1.46 

12-Sep-90 1.73 

13-Sep-90 1.12 

09-Oct-90 1.18 1.58 

10-Oct-90 2.29 
 TABLE 3. NORANDA LINE 3 ROOF DATA (lb TF/ton) 

8

11-Oct-90 3.26 

23-Oct-90 0.65 

24-Oct-90 0.87 

25-Oct-90 1.22 

06-Nov-90 1.42 1.31 

07-Nov-90 1.20 

11-Dec-90 1.37 1.75 

12-Dec-90 1.53 

13-Dec-90 2.34 

08-Jan-91 0.59 0.99 

09-Jan-91 1.31 

10-Jan-91 1.09 

05-Feb-91 0.75 0.92 

06-Feb-91 0.90 

07-Feb-91 1.10 

05-Mar-91 1.70 1.54 

06-Mar-91 1.20 

07-Mar-91 1.71 

09-Apr-91 0.78 1.16 

10-Apr-91 1.35 

11-Apr-91 1.34 

08-May-91 1.70 1.82 

09-May-91 2.15 

10-May-91 1.60 

10-Jun-91 1.47 1.56 

11-Jun-91 1.57 

12-Jun-91 1.63 

09-Jul-91 1.08 1.15 

10-Jul-91 1.39 

11-Jul-91 0.99 

12-Aug-91 0.74 0.72 
 TABLE 3. NORANDA LINE 3 ROOF DATA (lb TF/ton) 

9

12-Aug-91 0.76 

13-Aug-91 0.93 

13-Aug-91 0.54 

14-Aug-91 0.74 

14-Aug-91 0.64 

09-Sep-91 0.86 0.69 

09-Sep-91 0.54 

10-Sep-91 0.76 

11-Sep-91 0.70 

11-Sep-91 0.50 

12-Sep-91 0.92 

12-Sep-91 0.58 

07-Oct-91 0.89 0.95 

07-Oct-91 0.62 

08-Oct-91 0.73 

08-Oct-91 0.98 

09-Oct-91 1.09 

09-Oct-91 1.40 

05-Nov-91 0.45 0.79 

05-Nov-91 0.43 

06-Nov-91 0.79 

06-Nov-91 1.10 

07-Nov-91 0.99 

07-Nov-91 1.00 

09-Dec-91 0.89 0.80 

09-Dec-91 1.07 

10-Dec-91 0.94 

10-Dec-91 0.76 

11-Dec-91 0.57 

12-Dec-91 0.61 

06-Jan-92 1.04 0.90 
 TABLE 3. NORANDA LINE 3 ROOF DATA (lb TF/ton) 

10

07-Jan-92 0.62 

07-Jan-92 0.85 

08-Jan-92 0.81 

08-Jan-92 0.72 

09-Jan-92 1.36 

10-Feb-92 0.97 0.93 

10-Feb-92 0.50 

11-Feb-92 0.71 

11-Feb-92 1.29 

12-Feb-92 1.24 

12-Feb-92 0.85 

09-Mar-92 1.25 1.34 

09-Mar-92 1.56 

10-Mar-92 1.52 

10-Mar-92 1.04 

11-Mar-92 1.96 

11-Mar-92 0.73 

06-Apr-92 0.86 0.98 

06-Apr-92 0.95 

07-Apr-92 1.11 

07-Apr-92 0.49 

08-Apr-92 1.34 

08-Apr-92 1.15 

04-May-92 0.95 1.20 

05-May-92 1.91 

05-May-92 0.84 

06-May-92 1.18 

07-May-92 1.57 

07-May-92 0.76 

08-Jun-92 1.17 1.12 

08-Jun-92 0.95 
 TABLE 3. NORANDA LINE 3 ROOF DATA (lb TF/ton) 

11

09-Jun-92 1.55 

09-Jun-92 0.94 

10-Jun-92 1.33 

10-Jun-92 0.78 

06-Jul-92 0.85 0.66 

06-Jul-92 0.53 

07-Jul-92 0.75 

07-Jul-92 0.59 

08-Jul-92 0.75 

08-Jul-92 0.50 

12-Aug-92 0.69 1.00 

12-Aug-92 0.94 

13-Aug-92 1.02 

13-Aug-92 1.00 

14-Aug-92 1.34 

14-Aug-92 0.99 

08-Sep-92 0.86 0.87 

08-Sep-92 0.71 

09-Sep-92 1.04 

09-Sep-92 0.90 

10-Sep-92 1.00 

10-Sep-92 0.72 

05-Oct-92 1.03 1.15 

05-Oct-92 1.41 

06-Oct-92 0.99 

06-Oct-92 1.03 

07-Oct-92 1.30 

07-Oct-92 1.12 

09-Nov-92 0.98 0.78 

09-Nov-92 0.82 

10-Nov-92 0.62 
 TABLE 3. NORANDA LINE 3 ROOF DATA (lb TF/ton) 

12

10-Nov-92 0.56 

11-Nov-92 0.76 

11-Nov-92 0.95 

07-Dec-92 0.74 0.77 

07-Dec-92 0.58 

08-Dec-92 0.72 

09-Dec-92 0.59 

09-Dec-92 1.03 

10-Dec-92 0.96 

 AMTEST 1.01 0.91 

 0.83 

 0.90 

Summary: 

Avg 1.05 1.08 

Std 0.41 0.32 

N 192 46 

 Add 0.06 lb/t for primary system 
13

 TABLE 4. COLUMBIA FALLS ROOF DATA (TF in lb/ton) 

 SINGLE 3-RUN 

Run RUN AVG. 

1 2.75 2.40 

2 0.86 

3 3.58 

4 2.69 2.16 

5 1.88 

6 1.91 

7 2.04 1.93 

8 1.87 

9 1.89 

10 1.00 1.60 

11 2.24 

12 1.57 

13 1.29 1.63 

14 1.09 

15 2.52 

16 1.93 2.74 

17 2.77 

18 3.53 

19 2.33 2.34 

20 2.34 

 

 Avg. 2.12 

 Std. dev. 0.42 

 N 7 

 Add 0.095 lb/ton for primary system emissions. 
14

 TABLE 5. KAISER-TACOMA LINE 2 ROOF DATA (lb/t TF)

Date Single run Monthly avg 

Mar-93 2.13 2.12 

 1.75 

 2.47 

Apr-93 2.83 2.28 

 1.84 

 2.18 

May-93 1.23 1.56 

 1.60 

 1.86 

Jun-93 2.09 2.01 

 2.34 

 1.61 

Jul-93 2.12 1.97 

 1.56 

 2.24 

Aug-93 1.82 1.90 

 1.97 

 1.91 

Sep-93 2.03 2.30 

 2.42 

 2.45 

Oct-93 1.37 1.37 

 1.38 

 1.36 

Nov-93 1.76 2.11 

 1.92 

 2.66 

Dec-93 2.13 2.32 

 2.26 

 2.56 
15

Date Single run Monthly avg 

Jan-94 0.97 1.39 

 1.58 

 1.61 

Feb-94 1.43 1.54 

 1.76 

 1.44 

Mar-94 2.06 1.83 

 2.00 

 1.43 

Apr-94 2.30 2.13 

 2.13 

 1.95 

May-94 2.13 2.20 

 2.07 

 2.41 

Jun-94 2.23 2.02 

 1.89 

 1.93 

Jul-94 1.61 1.65 

 1.68 

Aug-94 2.06 2.01 

 2.25 

 1.72 

Sep-94 2.27 2.64 

 3.00 

Oct-94 2.04 2.45 

 2.86 

Nov-94 1.74 2.21 

 2.40 

 2.50 

Dec-94 2.09 2.46 
 TABLE 5. KAISER-TACOMA LINE 2 ROOF DATA 

16

 2.32 

 2.98 

Amtest 1.06 1.24 

(Mar-94) 2.12 

 0.55 

Avg 1.98 1.97 

Std dev. 0.47 0.36 

N 66 23 

Add 0.1 lb/t for the primary system 
17

 TABLE 6. KAISER-MEAD LINE 1 ROOF DATA (lb/ton TF)

Date Single run Monthly avg 

Aug-93 2.62 2.37 

 2.60 

 2.44 

 1.80 

Sep-93 2.98 2.90 

 2.64 

 2.56 

 1.60 

 4.74 

Oct-93 2.14 1.69 

 1.24 

 1.68 

 1.70 

Nov-93 1.10 1.38 

 1.62 

 1.04 

 1.76 

Dec-93 0.80 1.55 

 1.56 

 2.06 

 1.39 

 1.96 

Jan-94 2.14 2.02 

 1.78 

 2.04 

 2.12 

Feb-94 1.70 2.62 

 1.32 

 2.80 

 4.66 
18

Date Single run Monthly avg 

Mar-94 2.73 2.17 

 2.51 

 1.62 

 1.83 

Apr-94 1.84 2.04 

 1.09 

 2.72 

 2.51 

May-94 2.23 1.78 

 1.90 

 1.20 

Jun-94 1.91 1.79 

 1.92 

 1.60 

 1.84 

 1.67 

Jul-94 2.05 2.71 

 3.93 

 2.53 

 2.34 

Amtest 2.00 1.53 

(Mar-94) 1.38 

 1.20 

 

Avg 2.06 2.04 

Std dev. 0.78 0.49 

N 53 13 

Add 0.14 lb/ton to include primary system 
19

 TABLE 7. INDIVIDUAL RUN DATA FOR INTALCO LINE C (TF in lb/ton)

 Wet roof scrubbers Dry scrubbers 

 Month/year lb/ton Month/year lb/ton 

1 1990 0.40 1 1990 0.18 

1 1990 0.63 1 1990 0.48 

1 1990 0.72 1 1990 0.05 

1 1990 0.47 1 1990 0.09 

1 1990 0.66 2 1990 0.26 

1 1990 0.53 2 1990 0.09 

3 1990 0.72 2 1990 0.13 

3 1990 0.88 2 1990 0.19 

3 1990 0.73 3 1990 0.28 

3 1990 0.40 3 1990 0.29 

3 1990 0.68 3 1990 0.40 

3 1990 0.77 3 1990 0.73 

4 1990 0.81 4 1990 0.26 

4 1990 0.48 4 1990 0.25 

4 1990 0.71 4 1990 0.06 

4 1990 0.95 4 1990 0.14 

4 1990 0.62 5 1990 0.24 

4 1990 0.10 5 1990 0.05 

5 1990 0.47 5 1990 0.06 

5 1990 0.43 5 1990 0.14 

5 1990 0.34 6 1990 0.85 

5 1990 0.42 6 1990 0.10 

5 1990 0.44 6 1990 0.10 

5 1990 0.50 6 1990 0.03 

6 1990 0.45 7 1990 0.08 

6 1990 0.58 7 1990 0.18 

6 1990 0.81 7 1990 0.14 

6 1990 1.13 7 1990 0.10 

6 1990 0.48 8 1990 0.10 
20

 Wet roof scrubbers Dry scrubbers 

 Month/year lb/ton Month/year lb/ton 

6 1990 0.54 8 1990 0.06 

7 1990 0.86 8 1990 0.05 

7 1990 0.78 8 1990 0.21 

7 1990 0.75 9 1990 0.30 

7 1990 0.50 9 1990 0.10 

7 1990 0.49 9 1990 0.33 

7 1990 0.64 9 1990 0.12 

8 1990 1.10 10 1990 0.25 

8 1990 0.61 10 1990 0.08 

8 1990 0.82 10 1990 0.33 

8 1990 1.05 10 1990 0.15 

8 1990 0.65 11 1990 0.36 

8 1990 0.77 11 1990 0.17 

9 1990 0.55 11 1990 0.36 

9 1990 0.66 11 1990 0.21 

9 1990 0.54 12 1990 0.11 

9 1990 0.81 12 1990 0.20 

9 1990 0.72 12 1990 0.53 

9 1990 1.11 12 1990 0.43 

10 1990 1.10 1 1991 0.37 

10 1990 0.65 1 1991 0.13 

10 1990 0.71 1 1991 0.15 

10 1990 0.66 1 1991 0.37 

10 1990 0.44 2 1991 0.13 

10 1990 0.49 2 1991 0.14 

11 1990 0.42 2 1991 0.24 

11 1990 0.45 2 1991 0.42 

11 1990 0.49 3 1991 1.07 

11 1990 0.63 3 1991 0.63 

11 1990 0.42 3 1991 0.38 
TABLE 7. INDIVIDUAL RUN DATA FOR INTALCO LINE C (TF in lb/to

21

11 1990 0.50 3 1991 0.37 

12 1990 0.72 4 1991 0.29 

12 1990 0.47 4 1991 0.31 

12 1990 0.55 4 1991 0.07 

12 1990 0.79 4 1991 0.56 

12 1990 0.88 5 1991 0.29 

1 1991 0.80 5 1991 0.11 

 5 1991 0.14 

 5 1991 0.20 

 6 1991 0.24 

1 1991 0.53 6 1991 0.10 

1 1991 0.88 6 1991 0.26 

2 1991 0.63 6 1991 0.08 

2 1991 0.53 7 1991 0.32 

2 1991 0.94 7 1991 0.13 

2 1991 0.63 7 1991 0.32 

2 1991 0.85 7 1991 0.09 

2 1991 1.33 8 1991 0.16 

3 1991 0.26 8 1991 0.45 

3 1991 0.47 8 1991 0.54 

3 1991 0.71 8 1991 0.33 

3 1991 0.56 9 1991 0.76 

3 1991 0.48 9 1991 0.29 

3 1991 0.42 9 1991 0.40 

4 1991 0.49 9 1991 0.29 

4 1991 0.56 10 1991 0.56 

4 1991 1.00 10 1991 0.23 

4 1991 0.69 10 1991 0.50 

4 1991 0.64 10 1991 0.12 

4 1991 0.63 11 1991 0.14 

5 1991 0.51 11 1991 0.21 
TABLE 7. INDIVIDUAL RUN DATA FOR INTALCO LINE C (TF in lb/to

22

5 1991 0.28 11 1991 0.43 

5 1991 0.47 11 1991 0.16 

5 1991 0.71 12 1991 0.20 

5 1991 0.69 12 1991 0.32 

5 1991 0.56 12 1991 0.36 

6 1991 0.45 12 1991 0.65 

6 1991 0.50 1 1992 0.87 

6 1991 0.64 1 1992 0.20 

6 1991 0.51 1 1992 0.31 

6 1991 0.61 1 1992 0.23 

6 1991 0.49 2 1992 0.16 

7 1991 0.60 2 1992 0.46 

7 1991 0.40 2 1992 0.37 

7 1991 0.56 2 1992 0.12 

7 1991 0.53 3 1992 0.13 

7 1991 0.45 3 1992 0.23 

7 1991 0.51 3 1992 0.05 

8 1991 0.49 3 1992 0.16 

8 1991 0.50 4 1992 0.48 

8 1991 0.62 4 1992 0.05 

8 1991 0.48 4 1992 0.26 

8 1991 0.47 4 1992 0.23 

8 1991 0.42 5 1992 0.13 

9 1991 0.28 5 1992 0.05 

9 1991 0.42 5 1992 0.10 

9 1991 0.38 5 1992 0.07 

9 1991 0.47 6 1992 0.08 

9 1991 0.36 6 1992 0.19 

9 1991 0.43 6 1992 0.32 

10 1991 0.86 6 1992 0.03 

10 1991 0.71 7 1992 0.20 
TABLE 7. INDIVIDUAL RUN DATA FOR INTALCO LINE C (TF in lb/to

23

10 1991 0.91 7 1992 0.07 

10 1991 0.69 7 1992 0.20 

10 1991 0.73 7 1992 0.29 

10 1991 0.52 8 1992 0.18 

11 1991 0.54 8 1992 0.33 

11 1991 0.74 8 1992 0.07 

11 1991 0.53 8 1992 0.35 

11 1991 0.79 9 1992 0.23 

11 1991 0.56 9 1992 0.17 

11 1991 0.76 9 1992 0.06 

12 1991 0.66 9 1992 0.14 

12 1991 1.30 10 1992 0.09 

12 1991 1.16 10 1992 0.04 

12 1991 0.54 10 1992 0.02 

12 1991 0.48 10 1992 0.64 

12 1991 0.41 11 1992 0.03 

1 1992 0.58 11 1992 0.25 

1 1992 1.10 11 1992 0.13 

1 1992 0.62 11 1992 0.27 

1 1992 0.60 12 1992 0.28 

1 1992 0.67 12 1992 0.44 

1 1992 0.66 12 1992 0.12 

2 1992 0.52 12 1992 0.16 

2 1992 0.58 1 1993 0.74 

2 1992 0.84 1 1993 0.13 

2 1992 0.58 1 1993 0.31 

2 1992 0.59 1 1993 0.34 

2 1992 0.94 2 1993 0.02 

3 1992 0.47 2 1993 0.30 

3 1992 0.46 2 1993 0.21 

3 1992 0.60 2 1993 0.18 
TABLE 7. INDIVIDUAL RUN DATA FOR INTALCO LINE C (TF in lb/to

24

3 1992 0.41 3 1993 0.29 

3 1992 0.66 3 1993 0.47 

3 1992 0.60 3 1993 0.36 

4 1992 0.86 3 1993 0.78 

4 1992 0.34 4 1993 0.07 

4 1992 0.65 4 1993 0.17 

4 1992 0.49 4 1993 0.17 

4 1992 0.84 4 1993 0.12 

4 1992 0.62 5 1993 0.21 

5 1992 0.51 5 1993 0.31 

5 1992 0.84 5 1993 0.09 

5 1992 1.05 5 1993 0.20 

5 1992 0.56 6 1993 0.16 

5 1992 0.69 6 1993 0.66 

5 1992 0.14 6 1993 0.67 

6 1992 0.39 6 1993 0.78 

6 1992 0.46 7 1993 0.36 

6 1992 0.67 7 1993 0.15 

6 1992 0.38 7 1993 0.15 

6 1992 0.37 7 1993 0.15 

6 1992 0.47 8 1993 0.18 

7 1992 0.57 8 1993 0.32 

7 1992 0.46 8 1993 0.20 

7 1992 0.76 8 1993 1.24 

7 1992 0.62 9 1993 0.16 

7 1992 0.49 9 1993 3.44 

7 1992 0.77 9 1993 0.40 

8 1992 0.64 9 1993 0.31 

8 1992 1.84 9 1993 0.31 

8 1992 0.98 10 1993 0.14 

8 1992 0.43 10 1993 0.11 
TABLE 7. INDIVIDUAL RUN DATA FOR INTALCO LINE C (TF in lb/to

25

8 1992 0.42 10 1993 0.66 

8 1992 0.74 10 1993 0.13 

9 1992 0.44 11 1993 0.12 

9 1992 0.42 11 1993 0.25 

9 1992 0.80 11 1993 0.33 

9 1992 0.55 11 1993 0.35 

9 1992 0.46 12 1993 0.10 

9 1992 0.63 12 1993 0.05 

10 1992 0.88 12 1993 0.13 

10 1992 0.46 12 1993 0.07 

10 1992 0.65 

10 1992 0.68 Avg. 0.275 

10 1992 0.45 Std dev. 0.304 

10 1992 0.43 N 193 

12 1992 0.50 

12 1992 0.57 

12 1992 0.67 

1 1993 0.41 

1 1993 0.51 

1 1993 0.67 

1 1993 1.02 

1 1993 0.89 

3 1993 1.09 

3 1993 0.86 

3 1993 1.09 

3 1993 1.28 

3 1993 0.69 

4 1993 1.35 

4 1993 0.46 

4 1993 0.38 

4 1993 0.72 
TABLE 7. INDIVIDUAL RUN DATA FOR INTALCO LINE C (TF in lb/to

26

4 1993 0.77 

4 1993 0.69 

5 1993 1.31 

5 1993 0.07 

5 1993 1.57 

5 1993 1.55 

5 1993 0.94 

5 1993 0.90 

6 1993 0.97 

6 1993 0.75 

6 1993 0.15 

6 1993 1.37 

6 1993 0.55 

6 1993 0.54 

7 1993 0.94 

7 1993 0.62 

7 1993 1.05 

7 1993 0.82 

7 1993 0.51 

7 1993 0.03 

8 1993 0.57 

8 1993 0.50 

8 1993 0.39 

8 1993 0.51 

8 1993 0.55 

8 1993 0.43 

9 1993 1.17 

9 1993 0.69 

9 1993 0.87 

9 1993 0.72 

9 1993 0.75 
TABLE 7. INDIVIDUAL RUN DATA FOR INTALCO LINE C (TF in lb/to

27

9 1993 0.06 

10 1993 0.91 

10 1993 0.55 

10 1993 0.20 

10 1993 0.56 

10 1993 0.91 

10 1993 0.71 

11 1993 0.95 

11 1993 0.52 

11 1993 2.17 

11 1993 0.51 

12 1993 0.90 

12 1993 0.95 

12 1993 1.17 

12 1993 0.70 

12 1993 1.50 

12 1993 0.37 

Avg. 0.69 

Std dev. 0.37 

N 259 
28

 TABLE 8. INTALCO LINE C MONTHLY AVERAGES 

 (Monthly average for wet roof scrubbers 

 plus 12-month average for primary system) 

Month/year TF lb/ton 

1 1990 0.79 

3 1990 0.92 

4 1990 0.83 

5 1990 0.65 

6 1990 0.88 

7 1990 0.89 

8 1990 1.05 

9 1990 0.95 

10 1990 0.90 

11 1990 0.70 

12 1990 0.90 

1 1991 0.74 

2 1991 1.13 

3 1991 0.79 

4 1991 0.98 

5 1991 0.85 

6 1991 0.84 

7 1991 0.82 

8 1991 0.81 

9 1991 0.70 

10 1991 1.05 

11 1991 0.96 

12 1991 1.07 

1 1992 0.92 

2 1992 0.89 

3 1992 0.74 

4 1992 0.84 

5 1992 0.84 
29

Month/year TF lb/ton 

6 1992 0.67 

7 1992 0.82 

8 1992 1.05 

9 1992 0.76 

10 1992 0.80 

12 1992 0.79 

1 1993 1.13 

3 1993 1.36 

4 1993 1.09 

5 1993 1.42 

6 1993 1.08 

7 1993 1.02 

8 1993 0.85 

9 1993 1.07 

10 1993 1.00 

11 1993 1.40 

12 1993 1.29 

 

 Avg. 0.97 

 Std dev. 0.26 

 N 45 
30

 TABLE 9. SODERBERG POM DATA 

TACOMA POM DATA lb/ton 

 Line 2 Roof Dry scrubber 

 

 Single runs Avg 3 runs Single runs Avg 3 runs 

 lb/ton lb/ton lb/ton lb/ton 

March 94 1.76 1.71 2.52 1.60 

 1.78 1.21 

 1.58 1.06 

Oct 94 1.59 1.63 0.164 0.11 

 1.51 0.058 

 1.78 0.093 

 1.52 1.38 1.72 0.64 

 1.25 0.105 

 1.38 0.097 

 1.42 1.64 

 1.62 

 1.88 

 2.36 2.72 

 3.72 

 2.09 

 

Average 1.816 1.816 0.781 0.781 

Standard 0.598 0.522 0.899 0.756 

deviation 
31

N 15 5 9 3 
32

 TABLE 9. SODERBERG POM DATA (cont'd) 

POM in lb/ton for roof scrubbers 

Plant Fan Inlet POM Avg of 3 Outlet POM Avg of 3 

Columbia 9 1.610 0.90 0.365 0.18 

Aluminum 0.365 0.029 

 0.730 0.146 

 12 2.260 2.07 0.292 0.44 

 1.460 0.438 

 2.480 0.584 

 

Northwest 2 3.16 3.68 1.6430 1.42 

Aluminum 3.15 1.5730 

 4.74 1.0420 

 3 3.13 3.21 1.8800 2.19 

 3.13 2.0650 

 3.35 2.6160 

 2 4.76 3.45 3.0000 2.40 

 3.48 2.4000 

 2.12 1.8000 

 3 3.53 2.47 2.6800 1.88 

 2.54 1.8800 

 1.33 1.0800 

 

 Avg. 2.63 2.63 1.42 1.42 

 Std dev. 1.22 1.04 0.95 0.92 

 N 18 6 18 6 

 Maximum 4.76 3.68 3.00 2.40 

Tests of the primary control system at Northwest Aluminum from 3 runs showed POM emissions averaged only 0.0097 lb/ton (range of 

0.009 to 0.011 lb/ton). 
33
34

 TABLE 10. NORANDA BAKE FURNACE DATA 

 Total fluoride lb/ton anode 

 

 lb/ton 

 Avg of 3 runs 

 Alum. Anode Ln lb/ton Ln 

Sep 1983 0.018 0.036 -3.324 0.035 -3.362 

 0.017 0.034 -3.381 

Nov 1983 0.017 0.034 -3.381 

 0.011 0.022 -3.817 0.018 -4.017 

 0.011 0.022 -3.817 

Mar 1984 0.005 0.010 -4.605 

 0.004 0.008 -4.828 0.009 -4.748 

 0.004 0.008 -4.828 

Apr 1984 0.005 0.010 -4.605 

 0.005 0.010 -4.605 0.010 -4.605 

 0.005 0.010 -4.605 

May 1984 0.005 0.010 -4.605 

 0.026 0.052 -2.957 0.065 -2.728 

 0.067 0.134 -2.010 

Jun 1984 0.005 0.010 -4.605 

 0.011 0.022 -3.817 0.014 -4.269 

 0.004 0.008 -4.828 

Jul 1984 0.006 0.012 -4.423 

 0.026 0.052 -2.957 0.031 -3.463 

 0.018 0.036 -3.324 

Aug 1984 0.003 0.006 -5.116 

 0.003 0.006 -5.116 0.010 -4.605 

 0.003 0.006 -5.116 

Sep 1984 0.009 0.018 -4.017 

 0.005 0.010 -4.605 0.011 -4.480 

 0.007 0.014 -4.269 

Oct 1984 0.005 0.010 -4.605 
35

 Total fluoride lb/ton anode 

 

 lb/ton 

 Avg of 3 runs 

 Alum. Anode Ln lb/ton Ln 

 0.002 0.004 -5.521 0.004 -5.521 

 0.002 0.004 -5.521 

Nov 1984 0.002 0.004 -5.521 

 0.001 0.002 -6.215 0.006 -5.116 

 0.004 0.008 -4.828 

Dec 1984 0.004 0.008 -4.828 

 0.015 0.030 -3.507 0.019 -3.981 

Jan 1985 0.002 0.004 -5.521 

 0.011 0.022 -3.817 

Apr 1985 0.010 0.020 -3.912 0.011 -4.541 

Jun 1985 0.002 0.004 -5.521 

 0.004 0.008 -4.828 

 0.006 0.012 -4.423 0.024 -3.730 

Jan 1986 0.020 0.040 -3.219 

Feb 1986 0.010 0.020 -3.912 

Mar 1986 0.007 0.014 -4.269 0.019 -3.981 

 0.006 0.012 -4.423 

 0.015 0.030 -3.507 

Apr 1987 0.057 0.114 -2.172 0.059 -2.836 

May 1987 0.018 0.036 -3.324 

Jun 1987 0.013 0.026 -3.650 

 0.013 0.026 -3.650 0.061 -2.802 

 0.008 0.016 -4.135 

Jun 1988 0.070 0.140 -1.966 

Aug 1988 0.026 0.052 -2.957 0.497 -0.698 

Sep 1988 0.031 0.062 -2.781 

Oct 1988 0.689 1.378 0.321 

Nov 1988 0.032 0.064 -2.749 0.160 -1.833 
TABLE 10. NORANDA BAKE FUR

36

 0.041 0.082 -2.501 

 0.167 0.334 -1.097 

 0.526 1.052 0.051 0.362 -1.016 

 0.010 0.020 -3.912 

 0.007 0.014 -4.269 

Dec 1988 0.003 0.006 -5.116 0.035 -3.343 

Feb 1989 0.031 0.062 -2.781 

 0.019 0.038 -3.270 

Mar 1989 0.022 0.044 -3.124 0.120 -2.120 

 0.021 0.042 -3.170 

 0.137 0.274 -1.295 

Jul 1989 0.024 0.048 -3.037 0.078 -2.551 

Aug 1989 0.005 0.010 -4.605 

Jan 1990 0.088 0.176 -1.737 

Feb 1990 0.244 0.488 -0.717 0.417 -0.874 

 0.370 0.740 -0.301 

Apr 1990 0.012 0.024 -3.730 

 0.007 0.014 -4.269 0.013 -4.317 

May 1990 0.008 0.016 -4.135 

 0.005 0.010 -4.605 

 0.005 0.010 -4.605 0.022 -3.817 

Jan 1991 0.013 0.026 -3.650 

Aug 1991 0.015 0.030 -3.507 

 0.018 0.036 -3.324 0.024 -3.730 

Sep 1991 0.006 0.012 -4.423 

 0.012 0.024 -3.730 

 0.012 0.024 -3.730 0.038 -3.270 

Jan 1992 0.007 0.014 -4.269 

Feb 1992 0.038 0.076 -2.577 

Mar 1992 0.037 0.074 -2.604 0.034 -3.381 

Jul 1992 0.005 0.010 -4.605 
TABLE 10. NORANDA BAKE FUR

37

 0.009 0.018 -4.017 

Aug 1992 0.005 0.010 -4.605 0.014 -4.269 

 0.007 0.014 -4.269 

 0.009 0.018 -4.017 

May 1993 0.011 0.022 -3.817 0.023 -3.758 

Jun 1993 0.011 0.022 -3.817 

 0.013 0.026 -3.650 

Jul 1993 0.031 0.062 -2.781 0.048 -3.037 

 0.036 0.072 -2.631 

 0.005 0.010 -4.605 

AMTEST 0.054 -2.919 0.027 -3.612 

 0.016 -4.135 

 0.024 -3.730 

 0.014 -4.269 

 

 Avg. 0.070 -3.744 0.070 -3.467 

 Std dev. 0.191 1.199 0.118 1.154 

 N 100 100 33 33 
38

 TABLE 11. BAKE FURNACE DATA

 ALUMAX BAKE FURNACE--TOTAL FLUORIDE 

 Single runs Avg of 3 runs 

 lb/ton lb/ton 

1992 0.0036 0.0038 

 0.0042 

 0.0036 

1993 0.0232 0.0136 

 0.0114 

 0.0062 

1994 0.0040 0.0039 

 0.0042 

 0.0036 

 Avg 0.0071 0.0071 

 Std dev 0.0065 0.0056 

 KAISER-MEAD BAKE FURNACE (lb/ton anode) 

 POM TF 

 lb/ton lb/ton 

 0.168 0.006 

 0.166 0.019 

 0.148 0.015 

Avg. 0.161 0.013 

Std dev 0.011 0.007 

 NORANDA BAKE FURNACE 

 lb/t POM 

 0.038 

 0.020 

 0.016 

Avg. 0.025 

Std dev 0.012 
39

 REFERENCES

1.Data submitted by the Aluminum Association: "Total Fluoride 

Emission Assessment." Covers the period from January 1989 

through December 1992. Docket Item II-I-15. 1993.

2.R. Strieter, Aluminum Association, to S. Fruh, EPA:PPSG, May 1, 

1995, Enclosing comments on the draft Technical Support 

Document. 

 

3.W. Wooster, Columbia Aluminum Corporation, to T. Mix, 

Washington Department of Ecology, and S. Fruh, EPA:ISB, 

August 26, 1994, Enclosing fluoride emission data for each 

potline. Docket Item II-D-69 . 

4.D. Hart, Noranda Aluminum, to S Fruh, EPA:PPSG, November 8, 

1994. Submitting total fluoride data. 

5.Emission test report, Method 5/POM and 13B Testing, Noranda 

Aluminum, Inc., New Madrid, Missouri, September 14-20, 1994, 

vol. I, prepared by Amtest Air Quality, Inc., January 10, 

1995. Docket Item II-I-37. 

6.Data provided by D. Ryan, Columbia Falls Aluminum, to S. Fruh, 

EPA:PPSG. January 1995. 

7.B. Leber, Kaiser Aluminum, to S. Fruh, EPA:PPSG, March 1, 

1996, Transmitting fluoride data for Kaiser's Tacoma 

Potline 2. 

8.Emission test report, Method 5/POM and 13B Testing, vol. I, 

Kaiser Aluminum and Chemical Corporation, Tacoma, 

Washington, March 1-8, 1994, prepared by AmTest Air Quality, 

Inc. for Kaiser Aluminum, September 14, 1994. Docket 

Item II-I-29. 

9.Kaiser Aluminum, Ravenswood Aluminum, and Reynolds Metals 

Company, to EPA:OAQPS, July 27, 1994, Enclosing "Development 

of Clean Air Act Amendments 112(d) Hazardous Air Pollutant 

Standards for the Primary Aluminum Industry: Proposal for 

Setting Standards for Horizontal Stud Soderberg and

Centerwork Prebake - 2 Subcategories." Docket Item II-D-66. 

10.Emission test report, Method 5/POM and 13B Testing, Kaiser 

Aluminum and Chemical Corporation, Mead, Washington, March 

15-24, 1994, vol. I, prepared by AmTest Air Quality, Inc., 

November 9, 1994. Docket Item II-I-33. 
40

11.G. Scott, Intalco Aluminum Corporation, to M. Branscome, 

Research Triangle Institute, February 16, 1995, Enclosing 

computer run of all data from potline dry system and potline 

wet scrubber system for 1990-1993. Docket Item II-D-83. 

12. Reference 8. 

13.Emission test report, Method 5/POM and 13B Testing, vol. I, 

Columbia Aluminum Corporation, Goldendale, Washington, 

November 29 - December 2, 1994, prepared by AmTest Air 

Quality, Inc., June 9, 1995. 

14.G. May, Northwest Aluminum, to S. Fruh, EPA:PPSG, February 4, 

1996, Transmitting POM data. 

15.Emissions Measurement Test Report: Methylene Chloride 

Extractable Organic Sampling, Northwest Aluminum Company, 

The Dalles, Oregon, prepared by Entropy, Inc. for EPA:EMB, 

March 1994. Docket Item II-A-16. 

16. Reference 4. 

17.R. Pulley, Alumax, to M. Branscome, Research Triangle 

Institute, February 13, 1995, Transmitting bake oven 

scrubber emission sampling results. Docket Item II-D-81. 

18.Emission test report, Method 5/POM and 13B Testing of Anode 

Bake Furnace, Kaiser Aluminum and Chemical Corporation, 

Mead, Washington, May 2-5, 1994, prepared by AmTest Air 

Quality, Inc. for Washington Department of Ecology,

December 12, 1994. Docket Item II-I-35. 

19.Reference 5.